Azula is the princess of the Fire Nation, daughter of Fire Lord Ozai and Princess Ursa, and the younger sister and archenemy to Prince Zuko. She was a key enemy of Team Avatar, chasing Avatar Aang and her banished brother far across the Earth Kingdom accompanied her two best "friends" Mai and Ty Lee.
A Firebending prodigy, Azula is sadistic, manipulative and obsessed with power. She is a skilled tactician who orchestrated the Fire Nation victory over the Earth Kingdom capital Ba Sing Se and halted the invasion on Day of Black Sun.
Azula harbored deep mental instabilities, believing her mother favored Zuko over her. Raised by her father in an environment devoid of a mother-figure, Azula had to be nothing less than perfect in her father's eyes. After the betrayal of her two closest friends Mai and Ty Lee, these instabilities were brought up to the surface. Upon the arrival of Sozin's Comet, Azula was soon to be crowned Fire Lord; however, her defeat at the hands of her brother Zuko and Katara caused her to suffer a complete mental collapse.
Princess Azula was born to Prince Ozai and Princess Ursa about two years after her brother, Prince Zuko. She is named for her paternal grandfather, Fire Lord Azulon. Azula grew up in the riches, splendor, and privileges of being royalty in the Fire Nation. Her sharp wits and the fact that she is a Firebending prodigy gained great attention and acclaim, and quickly made her Ozai's favorite child. Her father began raising her as his true heir from an early stage, taking her into his confidence and grooming her in politics, while on the other hand ignoring Zuko. She later attended the Royal Fire Academy for Girls, where she befriendedMai and Ty Lee, two daughters of Fire Nation noblemen.
Even when she was only eight years old, Azula displayed her natural talents, along with her tendency for malice and perfection. When Ty Lee succeeded in performing a cartwheel after Azula had failed when attempting to do her own, Azula responded by shoving her friend to the ground and laughing gleefully. When she saw ten-year-old Mai attempting to hide her crush on her brother Zuko, Azula used her acting and cunning to convince her mother to make Zuko play with them. She then placed an apple on Mai's head and set it on fire, forcing Zuko to tackle her into a fountain to put out the fire.
A true megalomaniac, Azula desired power from a young age, suggesting that her father would make a better Fire Lord than the heir apparent, her Uncle Iroh. She is shown destroying a doll that her uncle had sent her as a gift from the Earth Kingdom. Not long after this, her cousin Lu Ten was killed, causing Iroh to abandon his legendary 600 day siege at Ba Sing Se, which in turn prompted Azula to dub him "a quitter and a loser". Shortly after receiving this news, Azula and the rest of her family went before Fire Lord Azulon, and she put on a spectacular display of her Firebending prowess. She then smugly watched Zuko try the same performance and fail. When Azulon sent everyone but Ozai out of the room, Azula took her brother and hid behind the curtains. From there, she watched her father request that he be made Fire Lord instead of Iroh. When Zuko fled in fear from the Fire Lord's anger, Azula stayed to watch with amusement. Azula then supposedly heard her grandfather sentence her brother to death, a fact that she wasted no time in gleefully reporting to the brother in question. She taunted him until her mother angrily pulled her away for a private talk. What happened after this is unknown, but Azula was next seen playing with the knife that Zuko had received from Iroh, and coolly announcing that their grandfather had passed away and their mother had vanished. Soon after, she was watching her father's coronation with glee. No love developed between her and Zuko throughout the next few years, as Ozai apparently began to favor her more and more over her brother during this period.
Azula, alongside Iroh and Zhao, watched Zuko's Agni Kai with his father. When Ozai burns her brother's face, she is seen smiling in triumph. When Zuko was banished from the Fire Nation, Azula officially became Ozai's heir. For the next three years, she would continue her relentless training in Firebending, strategy and combat, until she refined herself enough to serve her father. By this time her Firebending advances to the level where her fire is blue, thus increasing her overall bending power and intensity.
Book 1: Water
In Episode 12 of the Book of Water ("The Storm"), Azula makes a cameo during Iroh's story. When Zuko is forced into an Agni Kai with his father, Iroh watches in horror. To the right, Azula is watching the duel, smirking.
A New Mission
Shortly after Zhao's failed attack on the Northern Water Tribe, Azula is summoned by her father to his throne room. Kneeling before Fire Lord Ozai, he comments that Zuko is a failure and Iroh is a traitor, and charges her with a mission: to find and capture her uncle and brother. 
Book 2: Earth
A Family Reunion When Fire Lord Ozai branded Iroh a traitor and her brother Zuko a failure, she willingly obeyed her father's command for her to go and capture them, as seen in the final seconds of the first season finale. While en-route, she worked at perfecting her ability to create lightning, with the aid of her advisers and masters Lo and Li. Azula attempted to capture Zuko and Iroh, (now considered traitors to the Fire Nation) luring Zuko with the false promise of being accepted home with open arms. When Zuko learned of the deception, though, he attacked her. She easily evaded his attacks, and struck back with taunts and brief attacks. However, she failed to finish her brother off, as Iroh redirected her lightning attack away from Zuko and into a nearby cliff, and then kicked her off the edge of the ship. 
A New Target
After being counseled by her twin masters Lo and Li that the royal procession was not a wise choice to accompany her on her mission, she agreed and decided to abandon the unit, opting to find and recruit her two childhood friends. Ty Lee required some "convincing" as she had already started a life at the circus, but Mai was only too willing to leave the boredom of the conquered city of Omashu in favor of going on an exciting hunt especially if it involved interacting with her childhood crush Zuko. Whilst in the city, Azula met with Mai's father to 'discuss' matters of the city. She felt that he was failing his task of governing the city. After this she renamed Omashuas the city of New Ozai, in honor of her father.
During this episode, Azula first encountered the Avatar, Aang. She and her new allies were almost able to defeat Aang and his friends, but their overall unpreparedness, not being able to work as a team as well as a trump card delivered by a shrewd King Bumi enabled Team Avatar the time needed to escape the city. Soon after the battle she is seen leaving the city where she named the Avatar as a personal target in addition to capturing her brother and uncle. 
Princess Azula and her two friends are not seen again until they relentlessly pursued the Avatar's group, using a highly advanced Fire Nation tank train and three Mongoose Dragons as mounts to pursue them night and day. After wearing down the foursome, Azula decided they should split up, as Aang tried to lead Azula and her friends away from Sokka and Katara's trail. Azula noticed the deception, however, and sent Ty Lee and Mai to follow Sokka and Katara, while she continued chasing down the Avatar. Azula encountered the Avatar in an abandoned town and prepared to fight him; she was interrupted, though, by her brother Zuko, who had tracked them and had his own plans for capturing Aang. Azula fought the two boys, and despite the fact that both mostly concentrated on attacking her, she dominated the fight,easily landing a knockout blow on Zuko and later trapping Aang beneath some fallen rubble. Victory was denied to her, however, when Katara, Sokka, and Toph showed up to rescue Aang, while Iroh arrived to help Zuko. Cornered, she claimed to be willing to give in, saying that "a princess surrenders with honor", but to everyone's surprise and dismay, Azula took advantage of Iroh momentarily being off guard and seriously wounded him with a bolt of blue fire, then escaped as the four benders attacked with their respective elements. 
Azula was not seen again until she, along with her allies Mai and Ty Lee, were overseeing War Minister Qin's efforts to use a giant drill to break through the outer wall of Ba Sing Se. When the engineers reported an accident involving an ambushed engineer, stolen drill schematics, and further sabotage, Azula recognized that it was the work of the Avatar. Upon finding Aang, Katara, and Sokka attempting to break the engine's braces, Azula forced Aang and his gang to quickly flee. She sent Mai and Ty Lee after Katara and Sokka while Azula followed Aang, once again claiming personal ownership over the Avatar's capture. She caught Aang trying to bore a hole at the top of the drill, and they began a brutal match. Her firebending nearly overwhelmed the young Avatar, but he continued to fight as the drill bored its way through the wall. The fight ended in a rather undignified manner, with the drill's slurry water pipes bursting and Azula slipping into Aang; both of them almost fell off the drill. Azula tried to regain the advantage, but Aang was faster--by the time she had recovered, he was already on his way down the wall to destroy the drill. Azula gave one final strike with flame, but was a second too slow. Aang's powerful impact on the earthen wedge destroyed the drill and knocked Azula away.
Fall of Ba Sing Se
 Following this incident, Azula took Mai and Ty Lee and began hunting for the Avatar's bison, once again following his trail of hair. When the princess and her companions finally came across him in, he was in a forest clearing being tended to by a group of female warriors--the Kyoshi Warriors. After a few snide remarks in which she dismissed the warriors as the Avatar's "fan girls", Azula and her friends initiated a fight. Azula engaged Suki in a swift one-on-one battle and managed to disarm the warrior and kick her to the ground; however, she was distracted by another Kyoshi Warrior and turned to fight her instead. By the time she returned to Suki, Suki had already driven Appa off with a flaming branch. Suki then proceeded to take a firm stance, whereas Azula merely condescendingly teased her again, before rushing in to battle--the girls clashed, but the rest of the fight was left unseen. 
It was made clear that the Kyoshi Warriors did not claim victory in this battle--after the three girls dressed in Kyoshi Warrior uniforms were welcomed by the Earth King--and the leader of the girls was unmistakably Azula. 
Shortly after, The Earth King revealed that he had had a troubling week, with Long Feng and the Dai Li planning to take over. Azula's initial smug amusement at the irony of the situation turned to a sudden concern, though, when he revealed to them that the Earth Kingdom will invade the Fire Nation--on the day of a solar eclipse. Azula was visibly caught off-guard by this information, and immediately begins to consider what to do.
 After wards, she confided to Ty Lee and Mai that she planned to take control of the Dai Li and take down Ba Sing Se from the inside. She developed a plan to inform the Dai Li of their true nature, and thus spread the word on to their leader, Long Feng. The plan was successful, and Azula was taken by Dai Li agents in the middle of the night to Long Feng, who struck a deal with her. He gave her control of the Dai Li to overthrow the government in exchange for the Avatar.
Meanwhile, Katara discovered that Zuko and Iroh were in the city, and approached Azula, thinking her to be Suki, and informed her of her brother's presence. Azula revealed herself, and before Katara could warn anyone, Ty Lee took the young Waterbender down. Azula proceeded to lock her in the crystal catacombs beneath the city and have a "family reunion" by sending a letter to Iroh and Zuko, telling them that the Earth King wished for them to serve him tea.  Near the beginning of "The Crossroads of Destiny", the pair fell into her trap, and became surrounded by Dai Li agents. However, Iroh managed to escape them and the palace--Zuko, on the other hand, chose to stay behind to face Azula, challenging her to an Agni-Kai. His sister nonchalantly turned it down, and he was overwhelmed by the Dai Li. He was then imprisoned in the same dungeon as Katara.
Finally, Azula unleashed her coup upon the city, and the Dai Li arrested the Council of Five, the Earth King's highest ranking generals, while she personally captured the Earth King. Sokka and Toph were arrested as well while attempting to warn the Earth King of the danger, and Azula sent them off to a separate dungeon. Immediately afterward, Long Feng arrived on the scene and commanded the Dai Li to arrest Azula, smugly proclaiming a double-cross. The laugh was all Azula's, though, as she gleefully explained that the Dai Li were so impressed by her that they no longer knew who to follow. In fact earlier, a Dai Li agent had remarked to Long Feng that Azula was "both terrifying and inspirational at the same time"; a perfect example of her Machiavellian talents. In a smug and verbose speech, she denounced him for his lack of the divine right to rule--something she possessed and boasted about. She ended by commanding Long Feng to bow to her, since he could not compete with somebody born to rule. He grudgingly obliged, saying that she had beaten him at his own game. She scathingly replied that he was "never even a player". 
Battle in the Crystal Catacombs
 Azula appeared one last time in the chapter, shortly after Iroh and Aang found Katara and Zuko. Aang and Katara had been sent off by Iroh to find Sokka and Toph, while he remained behind for a moment with Zuko to bring him finally over to the side of good. However, his choice would not be complete without the devil upon his shoulder, and Azula was only too willing to play that part. Using the Dai Li to immobilize Iroh, she put her tongue and wit to the ultimate test, promising that their father would restore Zuko's honor and that she needed him--she promised him everything if he would help her. She closed the argument by leaving him to choose his own destiny and going after Katara and the Avatar. However, things were not going in her favor during the beginning of the battle, as her attacks could not break through their defense, and she found herself surrounded on both sides by Aang and Katara. Just when it seemed that she might lose the battle, her work came to fruition. Zuko arrived, and after a moment of consideration, chose to attack the Avatar. A long battle ensued and Azula attacked Katara only to be held back in a dire predicament, with one leg and one arm immobilized in water. Azula was saved by Zuko's timely intervention, and actually gave him an approving look before proceeding to fight the Avatar. After disabling him, she moved to end the stalemate between her brother and Katara. Together, she and Zuko easily overwhelmed the Waterbender. The Dai Li joined them within a few moments, and Azula and her brother appeared unstoppable.  Aang then closed himself off in a chamber of crystal; the rest of the room stared as he entered the Avatar State. However, Azula positioned herself behind the Avatar, and used her lightning to strike the Avatar in the back before he could unleash his own assault. She would have been the Avatar's killer if not for Katara's timely recovery and swift Waterbending; all the same, the Avatar was unable to fight, and Azula and Zuko were unquestionably the victors. As the siblings approached the defeated duo, though, they were blocked by the timely appearance of Iroh. He temporarily held off Azula, Zuko, and the Dai Li, allowing himself to be captured once Katara had made her escape with Aang. Later, in the throne room of the Earth King, Azula assures a concerned Zuko that he had restored his honor by joining her, and that Iroh had been the one who had betrayed him--not the other way around. His honor was restored, she explained--for after a hundred years, she and Zuko had finally conquered the Earth Kingdom city of Ba Sing Se. 
Book 3: Fire
 In "Going Home Again", a canonical interlude comic featured within the second All-Avatar Nick Mag Presents edition, Azula is shown making arrangements for their return to Fire Nation. One of which is passing her position as ruler of Ba Sing Se over to Joo Dee, whom she views as the perfect person to leave in her stead, dubbing the former tour guide Supreme Bureaucratic Administrator. Azula then refuses to take no as an answer when a reluctant Zuko chooses to remain in Ba Sing Se. Gathering Ty Lee, the princess schemes to use Mai and Zuko's mutual childhood crushes to entice her brother's decision. With the false report of a meeting with a Admiral Liang, she sets the two up on a Fire Nation-themed dinner date, featuring the Dai Li agents serving as waiters. However, the ruse is uncovered when Zuko overhears Azula and Ty Lee giggling in the nearby bushes. The princess attempts to catch herself, claiming that she was just telling Ty Lee to stop messing around in the bushes. Neither Zuko nor Mai buys into the tale and leave off on a private walk around Ba Sing Se.
The following day, while boarding the ships, Azula looks on at Zuko and Mai speaking affectionately with one another and concludes that her plan seems to have been quite successful after all. She then turns to her chained uncle and wonders aloud if the prisoner will even survive the trip home. As she bids her brother farewell, Zuko suddenly makes the resolve to come with them back to the Fire Nation. Azula slyly tells her brother to do whatever he wants, as it's his decision.
 Azula and Zuko return home and both are welcomed with open arms by the people, with a rally held in their honor to praise their successful efforts at the Earth Kingdom capital. Later at the old turtle duck pond, Azula and Zuko converse about Zuko's long-awaited meeting with their father. Zuko is anxious not only about the upcoming audience, but also that he must return to his father without the Avatar. Azula shrugs it off, once again restating her position that the debt is repaid by the Avatar being dead. At this, Zuko momentarily hesitates to agree in Aang's supposed demise. Azula however appears to disregard it and simply walks away.
When Zuko at last meets his father, it is revealed that Azula misinformed Ozai that he was the one who killed the Avatar. Perplexed, Zuko immediately goes to Azula's chamber to question her actions. Azula claims that she saw how worried Zuko was about not having the Avatar, she decided to give him the credit for his demise out of a generous gesture to repay his aid in the takeover of Ba Sing Se. Zuko refuses to believe her explanation, accusing her of retaining an ulterior motive. Azula nonchalantly points out how letting him have all the glory over slaying the Avatar could do little to benefit her, but insidiously acknowledges the fact that should it be discovered that the Avatar was indeed alive, all that glory would swiftly turn into shame and foolishness. She assures Zuko that he has nothing to worry about, as he already said himself, there's no way the Avatar could have survived. With that, the princess bids her deeply incensed brother goodnight. 
 Azula, Mai, Ty Lee, and Zuko all travel to Ember Island for a brief vacation while the Fire Lord confers with his advisers in private. Azula takes advantage of this opportunity to experience life as a normal person for the very first time, choosing to keep her and Zuko's true identity a secret. At the beach Chan and his friend, Ruon-Jian, are impressed by Ty Lee and Mai. The two decide to invite Ty Lee and Mai to a party at Chan's house. Azula then interrupts Chan by insisting that she and Zuko are invited also. When Azula and the others arrive at his house, Azula mentions that his "sharp" outfit is so sharp that it "could puncture the hull of an Empire Class Fire Nation battleship leaving thousands to drown at sea." This "compliment" weirds out Chan and he awkwardly thanks her. Later, after shooting down Ty Lee confines in her that she needed help talking to boys. After very short and awkward lessons, Azula insists that Chan give her a tour of the house. He leads her out onto the deck and starts making a few jokes. Chan then moves in and kisses Azula. He then calls her pretty and she replies "Together, you and I will be the strongest couple in the entire world! We will dominate the earth!", coupled with a small display of her unique blue flames. Chan then makes an excuse to leave. Later, Azula plays the role of interpreter as the group takes turns telling stories which provide deep insight about how their lives have been. When her turn comes, Azula states she doesn't have a "pathetic sob story". However, she does softly admit that she was aware that her mother loved Zuko more and thought she was a monster, but callously adds that her mother was right, but it still hurt. It is later on hinted that Azula harbors repressed feelings of rage towards her mother for this. For the first time, she is seen as almost completely vulnerable and almost seems to have resigned herself to what she is in the absence of her mother. As a testament of their special day, Azula proceeds to lead the others into disrupting the party and trashing Chan's home. 
Azula, along with her father, brother, and all the high-ranking military officials in the Fire Nation, attends an important all-day war meeting. It is later revealed that, at that meeting, Azula was the one who suggested burning to ashes the entire Earth Kingdom using the power of Sozin's Comet, a plan that Ozai readily adopted, much to Zuko's dismay. 
The Day of Black Sun
 A few minutes after the beginning of the solar eclipse, as the Avatar, Toph, and Sokka manage to locate and burst into the Fire Lord's underground room, they are confounded to instead find Azula. She reveals that she's known about the invasion for months and is fully prepared to face and delay the attackers. Azula has two Dai Li agents she brought back from Ba Sing Se attack the trio while she runs away, closely pursued by Aang, Sokka and Toph. Once the agents have been defeated and Azula is cornered, Sokka realizes that she's merely wasting their time and that they should just forget her in favor of searching for Ozai. As they start to leave, Azula mentions Suki to Sokka, stating that she gave up hope on him ever rescuing her from her imprisonment. This revelation promptly makes Sokka charge at her in blind rage. Azula pulls out a shuriken, but Toph senses it and pins her to the wall. Sokka furiously demands to know where Suki is while Azula simply remains silent. When the eclipse ends, Azula breaks her restraints and coyly informs the trio of Ozai's precise location before running down the hall. As the invasion draws to a close, the princess is shown observing the Avatar and his friends escape aboard Appa from herairship. However, she chooses not give pursuit, knowing that sooner or later, they'll be back. 
During Azula's confrontation with the group, Zuko confronts his father, Ozai, and tells him that Azula lied to him by saying that Zuko killed the Avatar, when in reality Azula struck down the Avatar but he managed to survive in the end. Ironically, Ozai seems to have pardoned his daughter for these crimes, as in "The Boiling Rock, Part 2" she evidently has not faced punishment. Azula may have manipulated him once again.
Azula arrives at the prison with Ty Lee and Mai (who does not accompany her, but instead visits Zuko). The Princess interrupts the Warden's interrogation of the guard who is accused of taking part in a failed prison-escape attempt, only to inform him of his mistake i.e. the guard was not one of the group she was sure was responsible for the escape plan: Team Avatar.
She and Ty Lee later battle Sokka, Suki, and Zuko on the gondola. While Ty Lee fights Suki, Azula takes on Zuko and Sokka. Zuko manages to block her fire blasts, while Sokka moves in to strike her with his sword. Yet, despite their efforts, neither Zuko nor Sokka manage to defeat her. As the guards are about to cut the lines and drop the gondola into the boiling lake below, she and Ty Lee back flip to the other gondola. Much to her dismay, she finds her friend Mai defeating the guards to save Zuko and his friends.
 After the battle, she tells Mai that she should not have saved Zuko, since she knew the consequences. However, Mai tells Azula that she miscalculated, and she now loves Zuko more than she fears Azula. The idea of an emotion she has probably never experienced being stronger than her ability to instill fear and control sends her over the edge. As the tension rises, Azula and Mai are about to fight, but just before Azula can attack, Ty Lee suddenly blocks off two of her chi paths and paralyzes her, much to the surprise of all three of the girls. The guards come to Azula's aid, and she tells the guards to put Ty Lee and Mai where she can never see their faces again, and "let them rot".
This marks an important turning point in her life because following the betrayal of her friends, Mai and Ty Lee, she never displays her cold merciless precision and clarity of mind again. It's possible that she considered them to be the only friends she had ever had, and that it seemed to her that Zuko had stolen them from her. 
 A few days after her defeat at the Boiling Rock, Azula tracked Zuko and Sokka down to the Western Air Temple. She attacked with a full fleet of airships, and was intent on killing Zuko more than ever before; claiming to about to be celebrating herself becoming an only child. Zuko attacks, creating a diversion while Aang and the others escape. As the battle progresses, Zuko and Azula seem evenly matched until the fight is abruptly ended when their flaming fists meet one another (resulting in an explosion) and they are both thrown backwards off the airship. Zuko is saved from falling to his death by Appa and Team Avatar while Azula propels herself (using firebending) to safety and latches onto the nearby cliff-side. 
The Ember Island Players
In the play her character shows no signs of her cruelty likely due to propaganda. However, at the end of the play her character kills Zuko's character to wild cheers, which leaves the real Zuko looking taken aback. 
Descent into Madness
 When Ozai crowned himself Phoenix King, he appointed Azula to be the new Fire Lord (after a short discussion in which Azula felt he was looking down on her in the same way he did to Zuko). Azula, however, had already begun to lose her grip on reality and her father not wanting her with him only made it worse.  She began banishing her subjects out of fear and paranoia, including a servant for leaving a pit in her cherries, which she took as a crime against her life, the Dai Li for taking five minutes to arrive after being summoned (during which she believed "an assassin could have done away [with her] and been on his merry way"), and the Imperial Firebenders. When Lo and Li confronted the Princess on her well being, she became enraged, and told the twins they must have an Agni Kai. When Lo and Li said they couldn't because they weren't Firebenders, Azula banished Lo while pointing at Li, confusing them as to who was banished. With all her subjects banished, she attempted to fix her hair herself. She failed, and instead cut off a large portion of her trademark bangs. It also appeared that she wasn't sleeping well as she had dark circles under her eyes by this point, possibly afraid someone might kill her while sleeping. She was also haunted by a hallucination of her mother. In her hallucination, her mother showed sorrow as her daughter was, in her mind, confused. After Ursa told Azula she loved her, Azula threw her hairbrush at her mirror in a fit of emotional rage, ending the hallucination. Azula then fell to her knees bitterly sobbing to herself.   Her coronation, without the Fire Nation subjects and only the Fire Sages that are present, was interrupted by her brother and Katara. When Zuko proclaimed that he would be Fire Lord. Azula challenged Zuko to an Agni Kai, which Zuko accepted, noticing that something was off about her. At first, they seemed to be evenly matched, but as Azula continued to slip into insanity, she began to wear herself out. This was evident when Zuko managed to strike her down once despite her enraged and advanced moves. Zuko taunted her, declaring she was afraid to hit him with lightning. Azula took the bait, shouting "I'll show you lightning!" She first aimed at Zuko, but then realized Katara was vulnerable and shot at her instead. Zuko jumped in the way and took the lightning bolt head-on trying to redirect it in mid-air. Even though he succeeded, some of it still remained in his body, seriously harming him and removing him from the fight.  Azula then moved on to Katara, who is distraught over Zuko's injury. Azula did her best to keep Katara away from any water and frequently insulted the duo, calling her a filthy peasant, and saying "Zuzu, you don't look so good." Katara eventually immobilized her in a frozen splash of water from an underground canal and used the opportunity to chain her to the floor. When Azula saw her brother stand up alive, she finally broke. She began to breathe fire in a fit of rage while rolling around the floor, screaming and crying uncontrollably. Reduced to this feral state, she was completely lost within her own madness. She was no longer the composed, calculated and methodical princess she once was, finally descending into pure insanity. 
After her Agni Kai, Azula was transferred to a mental health facility on a nearby island where she was monitored around the clock.
The Last Airbender
In the M. Night Shamylan movie based on the first season, Azula only appears twice. She appeared as a child, laughing at Zuko when he faced his father in an Agni Kai and again at the very end while her father is briefing her on her new assignment: capture Aang, Zuko, and Iroh. Azula is played by Summer Bishil.
Like her father, Azula hungers for personal power and is a dedicated nationalist. Harboring a high intolerance of imperfection, Azula relentlessly drills herself towards perfection and settles for nothing less from herself or those that serve her. She believes that power and domination are what makes a person strong. She has absolute confidence in her"divine right to rule" which she believes she was born with. She has neither pity nor mercy towards those she marks as treasonous or inferior.
 Azula is marked by a distinct lack of empathy. Even as a child, she was seen to react with hostility when outdone, when she shoved Ty Lee to the ground after Ty Lee had ousted her in gymnastics. This behavior would characterize her relationship with her friends for many years. Although she could show sympathy towards them, she never cared for their feelings and manipulated them as she saw fit, such as when she threatened Ty Lee into leaving the circus and joining her cause. She is prone to asserting herself and her authority in a grandiose way, such as when she humiliated Long Feng in front of his former henchmen, or when she threatened the captain of her ship. She also shows a need for admiration from her father, whom she emulates to a great degree, and to a lesser extent from everyone else around her. She is shown reacting with despair and rage when she learned her father was going to the Earth Kingdom without her. She also becomes very violent (burning down a house) when rejected romantically by Chan. These are all traits of a Narcissistic Personality Disorder while her lack of empathy as a child and purposeful harming of animals is a sign of Conduct disorder.
Azula is marked as one of the cruelest characters in the series. From a very young age, Azula demonstrated sadistic aggression and a near total lack of remorse to friends, servants, family, and animals which suggests that she could be suffering from an antisocial personality disorder. Her own mother, Princess Ursa once remarked, "What is wrong with that child?” after observing her casual cruelties. Her first reaction to hearing of Iroh's son's death was to wonder whether this now makes her father the heir to the throne. She later dismisses her uncle as a quitter and a loser when learning he had ended his two year siege of Ba Sing Se to grieve for Lu Ten. She eagerly watches Azulon proclaim Ozai's punishment for trying to claim the throne and grins maliciously when Zuko is burned and scarred by their father. She also did not seem to care when her mother disappeared or her grandfather died. Her cruelty is apparently infamous and extreme; when Iroh accidentally ingests the poisonous White Jade flower, both he and Zuko quickly decide that they would rather go seek help from the Earth Kingdom and face certain death than deal with the Fire Nation and be handed over to Azula.
 Azula's characteristic blue flames symbolize the power she possesses and constantly seeks to increase. Her apathy also accounts for her ability to create and direct lightning, the "cold-blooded fire". According to Iroh, the skill requires complete control of all emotion, which would not prove difficult for Azula with her one-track mentality. Because of these skills, she is also an excellent tactician, regularly displaying cunning, perception, and resourcefulness that allows her to take advantage of almost any situation. She possesses good self control, facing down Long Feng and deceiving him when held captive, and can lie with a straight face and no physical reactions.
Ironically, for all her refinement and self-confidence, Azula does retain some insecurity. As a result of her sequestered life of royalty, she has developed a considerable amount of social ineptitude, particularly in her uncertainty of how to act around boys, and she frequently intimidates them during conversation. Her overly competitive nature surfaces during a Kuai Ballgame, and she later admits her jealously over how much attention Ty Lee receives from others.
However, in "The Boiling Rock, Part 2", Azula begins to show signs of a fragile mentality. As stated above, for all of her self-assurance, she is, for a moment, driven into rage when Mai betrayed her by helping Zuko to escape, and admitted to loving him more than she feared Azula. As Azula moved to strike her down, she was in turn temporarily paralyzed by Ty Lee. The enraged princess then orders both her former friends to be locked away and "left to rot". While it was apparent that Azula held herself in high regard above her friends, their sudden betrayal drove her to the edge for an instant, hinting just how unstable she might be.
 Azula's mentality continued to crumble as the series progressed. When she attacked Zuko and the gang at the Western Air Temple during "The Southern Raiders", Azula is evidently losing her sanity, as her attacks become far more vicious and is now obsessed with killing Zuko. During her father's coronation as Phoenix King during "Sozin's Comet, Part 1: The Phoenix King", Azula is told she will not assist in the attack on the Earth Kingdom. Azula seems distraught at this and takes this decision as an offense to her and her honor. However, she is more than happy to receive the title of Fire Lord.
In the day preceding her coronation, Azula became excessively paranoid, banishing all of her subjects for minor or suspected offenses. When she styles her hair for the coronation, she is so frustrated by her inability to tie up her hair bun that she cuts away her trademark bangs, leaving her hair a tattered mess. She then sees her mother in her mirror in an apparent hallucination. Her mother compliments her, saying that she always had beautiful hair. Azula then asks her mother why she was there, and Ursa tells her that she wouldn't miss her daughter's coronation. Azula tells her not to pretend to act proud, stating that she knew her mother thought she was a monster. The hallucination of her mother then tells her that she doesn't think that, that Azula is just confused, and that she loves her. Azula then goes deeper into insanity, throws her brush at the mirror, breaking it, and breaks down crying. She didn't seem surprised by her hallucination, implying it might not have been the first one.
 This incident exposes a complex facet to Azula's persona. Although outwardly maintaining a cold and dismissive opinion of her mother as witnessed in the episode "The Beach", Ursa's banishment ultimately had a devastating impact upon Azula's fragile psyche, possibly even more so than it did her brother Zuko. As Azula's sanity began slipping away from her, this inability to reconcile her perceived belief that Ursa considered her a monster with the truer (though idealized) maternal feelings of love and support that Ursa demonstrated in the hallucination created an inescapable conflict in her mind that furthered Azula's eventual mental collapse. Another thread to this argument is that Azula may have harbored a guilt-ridden conscience, long suppressed or held at bay for many years by her indominable will, but now rearing itself stronger than before in the form of her mother Ursa (whose love and guidance she secretly longed for but could never have) and whose gentle, motherly concerns over Azula's use of fear and cruelty as her only means of maintaining relationships with friends and family alike induces a violent near mental breakdown prior to her coronation.
It would also seem that in her ever increasing insanity, Azula gave into her fear of being killed. She accused her servant of purposely leaving a pit in her cherry so that she'll choke. She gets mad at the Dai Li when they arrive five minutes late, suggesting an assassin could sneak in, kill her, and "be on his merry way". She then suggests that the Dai Li could betray and kill her ("just like Mai and Ty Lee"), and banishes them. She then begins keeping her back against one of the throne's canopy poles, probably out of fear of being attacked or killed from behind.
It also appears that she wasn't sleeping well as she had dark circles under her eyes, implying that she might have feared someone killing her in her sleep. Upon Lo and Li's arrival to counsel her, Azula's fear of disappointing her father is clear and becomes so enraged when her old mentors' question her wishes that she momentarily forgets that they are not Firebenders.
Azula shows up at her coronation impatient and with her hair still a mess. Katara and Zuko then arrive to fight her, and she constantly provokes the duo as she attacks them. When Katara finally defeats Azula and chains her to the ground, Azula screams in anger and breathes fire uncontrollably, struggling to break herself free in extreme rage, falling into complete insanity. She drags herself along the ground helplessly, as Zuko and Katara look on in pity and horror. Throughout the series, Azula appeared to be unaffected by her failure to kill the Avatar, but her failed relationship with her mother (and her jealousy towards Zuko for receiving more of their mother's affection) coupled with the betrayal she suffered at the hands of Mai and Ty Lee (who were the closest persons in her entourage) and her subsequent defeat by Zuko and Katara, finally sends Azula over the edge as she cracks, screaming and crying uncontrollably. Azula is currently in a mental health facility on a nearby island in the Fire Nation where she is closely monitored.
Azula is one of the most skilled Firebenders in the series, and has been described as a "prodigy" by both Ozai and Zuko.
 The most noticeable feature of Princess Azula's bending is her ability to create her characteristic blue flames, which are much more intense than the red, orange and yellow fire normally used by Firebenders. Azula is only seen bending normal fire during her childhood and in the opening sequence. In "Return to Omashu", Azula was seen using flames in previously unseen ways, such as jets of flames, whirling disks, and blades of fire. Also notable is her ability to produce a greater amount of flames than most Firebenders without tiring, as she is shown to be able to maintain successive assaults for long durations of time.
She has also demonstrated the skill to condense her flames, enabling her fire to cut clean through various objects. When formed into fireballs, the flames serve to be rather concussive, able to firmly pulverize objects such as stone. Azula is able to generate powerful shields of swirling flames which can withstand the full force of four simultaneous elemental attacks (and a boomerang). She is even able to charge up her fire before releasing it, as was seen during her fight with Aang in "The Drill". In "Appa's Lost Days", Azula fights off multiple Kyoshi Warriors, using both Firebending and hand-to-hand techniques, and duels Suki. The outcome of this fight is not shown, but the fact Azula, Mai and Ty Lee infiltrated Ba Sing Se posing as the Kyoshi Warriors reveals that Azula won.
 The depth of Azula's potential seen thus far came in "The Crossroads of Destiny", where she is shown using very advanced techniques, creating large blasts of flame, evaporating a wave of water that Katara threw at her, using her flames to propel herself forward like a jet and minutes later produce and guide lightning. While little of her Firebending was seen in in the earlier stages of Book 3, she does demonstrate her powers a few times. In "The Beach", she uses Firebending to give extra propulsion in a game of Kuai Ball, creating an explosion and burning the net. In "The Day of Black Sun, Part 2: The Eclipse", she uses her Firebending to break free of her shackles, and briefly attacking Sokka, Aang and Toph. In "The Boiling Rock, Part 2" Azula engages a pitched battle with Zuko and Sokka, where she was still able to battle on equal footing with them despite her being outnumbered. In addition to creating her usual powerful fire balls, she is able to shoot her flames behind her in order to propel herself through the air onto the gondola.
Azula is one of the most powerful Firebenders in the entire series. Only Iroh and Ozai are clearly more powerful than she is, although Zuko is shown to be on approximately equal footing with her towards the end of the series and it is unknown how well Aang would have compared to her, but it is thought once Aang masters Firebending, he would overpower for he is the Avatar. It is also unknown how Jeong Jeong would've compared to her. Azula's Firebending powers and prodigious skill allow her to fend off many attackers with little effort, and, as is seen in "The Crossroads of Destiny", defeat a single talented bender, like Aang.
Azula is proficient in the highly difficult technique of creating and guiding lightning, a sub-skill of Firebending, and was the first character within the series to demonstrate the ability.
 As Azula gradually lost her sanity prior to the arrival of Sozin's Comet, her firebending became unfocused and wild, making her all the more dangerous, however it also resulted in her becoming exhausted more easily then usual. Despite her state of mind, her attacks on Zuko and Katara during her final duel proved ferocious and destructive, and was still able to fire lightning accurately. However, her mental instability still weakened her battlefield prowess, and this ultimately resulted in her defeat at the hands of Katara. She displayed the ability to breathe fire as she struggled against her chains, but this was only brought about by her madness and rage in her defeat. She can also make fire come out of her nose and ears, but this was most likely due to the power of the comet and her complete mental breakdown.
Azula's skills in unarmed combat are displayed several times during the series, most prominently in "The Avatar State", "Appa's Lost Days", and "The Day of Black Sun". She easily avoided Zuko's frenzied knife attacks without the use of Firebending, guiding his hands off course. Later, she proceeded to disarm Suki, and knocked her off her feet without bending. She also has some skill with hidden weaponry, as she has shown the intent to use them during the eclipse. Her acrobatics and use of a hidden shuriken knife are apparently skills she picked up from Ty Lee and Mai, respectively. Azula is very agile and in "The Day of Black Sun", she has been shown to run up walls and do mid-air twirls. She dodged Aang and Toph's bending attacks with little to no effort using high jumps like Ty Lee. Her physical strength is also surprising as she can support her body in a horizontal position with just her arms with little effort.
 Azula has been shown to be an extremely cunning strategist. When she was a child, she demonstrated her military knowledge by successfully recounting Fire Lord Sozin's strategy in an old battle. In "The Avatar State", she plans a trap for Iroh and Zuko, which is only accidentally foiled by the captain of her ship. In "The Chase", she immediately discerns the Avatar's plan to mislead her with a false trail. In "The Guru" and "The Crossroads of Destiny", she plans and carries out a coup against the Earth King, winning Ba Sing Se for the Fire Nation. In "Nightmares and Daydreams", she participates in a war meeting with her father and brother. During The Day of Black Sun, she lays a trap for Aang and his friends using Dai Li agents in the Fire Lord's throne room, ensuring that the Eclipse time is used up. She also displays the ability to be so extremely capable of lying effectively that even Toph can't sense it when she does, showing that Azula doesn't feel remorse for lying or many of her other actions. In "The Boiling Rock, Part 2" she also displayed an innate ability to tell whether someone was telling the truth or not (almost like Toph), stating simply that she was a "people person".
Azula's intelligence makes her very skillful in manipulating people. She has used this skill on many people, including her brother Zuko, her mother Ursa, Long Feng, the Dai Li, Sokka and even her father.