Azula

Azula is one of the three main antagonists in the season 2 (alongside Ozai and her brother Zuko) and the secondary antagonist in season 3 of Avatar: The Last Airbender, and the token evil teammate in it's following comic books Avatar: The Search. She is the princess of the Fire Nation, and daughter of Fire Lord Ozai and his wife, princess Ursa. She is one of the main enemies for "Team Avatar" and for her banished brother, prince Zuko. Later in the series, she begins to lose her calm and cool nature and slips into insanity. In the series finale, her brother and Katara of the Water Tribe team up and defeat her in one of the last battles in the series.

After her defeat, she became mentally ill and had a nervous breakdown and went crazy, as she was not only defeated in battle, but also failed to defeat her brother. According to Nickelodeon, Zuko took pity on his sister and sent her to a mental facility. It is unknown if she is still alive during the events of The Legend of Korra, which takes place 70 years later.

Origin
Azula was born to Fire Lord Ozai and Princess Ursa. She was born 2 years after her brother Zuko. She was named after her grandfather, Fire Lord Azulon. She lived an extremely rich life and was spoiled but wasn't sheltered by any means. She was discovered to be a fire bending prodigy at a very young age, which made her Ozai's favorite child. He started teaching her about politics and how to be a successful ruler while ignoring Zuko. She went to the Royal Fire Academy for Girls, where she first met her best (and only) friends Mai and Ty Lee.

Personality
Azula relentlessly drilled herself toward perfection and settled for nothing less from herself or those who serve her. She believed that power and domination are what makes a person strong. She had absolute confidence in her "divine right to rule" which she believed she was born with. She had neither pity nor mercy toward those she marked as treasonous or inferior.

Azula was 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 bested her in gymnastics. This behavior would characterize her relationship with her friends for many years. Although she could show sympathy toward 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 was 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 showed a need for admiration from her father, whom she emulated to a great degree, and to a lesser extent from everyone else around her. She was shown reacting with despair and rage when she learned her father was going to the Earth Kingdom without her.

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 would choke. She got angry at the Dai Li when they arrived five minutes late, suggesting that in that time an assassin could sneak in, kill her, and "be on his merry way". She then suggested that the Dai Li could betray and kill her ("just like Mai and Ty Lee"), and banished them. She also began keeping her back against one of the throne's canopy poles as often as possible, probably out of fear of being attacked or killed from behind.

It also appeared that she was not sleeping well, as she had dark circles under her eyes. Upon Lo and Li's arrival to counsel her, Azula's fear of disappointing her father was clear. Azula became so enraged when her old mentors' questioned her wishes that she momentarily forgot that they were not firebenders, and ordered them to fight an Agni Kai with each other.

Azula showed up at her coronation impatient and with her hair a mess. Katara and Zuko then arrived to fight her, and she constantly provoked the duo as she attacked them. When Katara finally defeated Azula and chained her to the ground, Azula screamed in anger and breathed fire uncontrollably, furiously struggling to break herself free, falling into complete insanity. She dragged herself along the ground helplessly, as Zuko and Katara looked on in pity and horror. Azula appeared to be unaffected by her failure to kill the Avatar. However, her failed relationship with her mother (and her jealousy toward 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 sent Azula over the edge as she cracked, screaming and crying uncontrollably. Azula was admitted into a mental health facility on a nearby island in the Fire Nation, where she was closely monitored and observed.

A year later she is still in the mental facility and still seeing her delusion vision of her mother in mirrors. Zuko visits her, and asks her to try and coax the whereabouts of their mother out of Ozai. She accepts, but on the condition that she should be able to travel with Zuko to find their mother. Zuko accepts her terms and Azula is able to get their father to reveal an archive of intercepted letters from their mother to her former home. She discovers a letter that seemingly reveals that Zuko is not of royal blood, saying: "My dearest Ikem, It's taken me a long time to admit it, but you were right. I belong with you, and nothing is worth this pain. My one consolation is our son Zuko. When I look into his eyes, it's as if I'm looking into yours. My thoughts are with you always." With this information, Azula comes to the conclusion that she, being the only one with actual royal blood, should be in the throne in place of Zuko. She continues on the quest, however, because of her increasing paranoia that her mother is conspiring against her, and that if she were to Ursa, she could be rid of her for good.

When Ursa's location and new identity is reveled to her, she quickly makes her way there and confronts her, and attacking her. She is also enraged that Ursa, as Noriko, had had another daughter: Kiyi. Eventually  Zuko was able to keep her down, and Ursa apologized to Azula, saying that she did not love her properly or enough. She almost struck her down until Zuko intervened, though he refused to kill her. Realizing that Zuko still considers her as family no matter what, Azula runs off into the forest. She is currently MIA.

Firebending
Azula was one of the most skilled firebenders of her time, recognized as a prodigy by both Ozai and Zuko. The most noticeable feature of Princess Azula's bending was 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 was only seen bending normal fire during her childhood (and in the opening sequence). Azula also used her flames in previously unseen ways, such as jets of flames, whirling disks, and blades of fire. She often firebends using only two fingers, rather than a closed fist or open hand common to other firebenders. Also notable was her ability to produce a greater amount of flames than most firebenders without tiring, as she was shown to be able to maintain successive assaults for long durations of time.

She had also demonstrated the skill to condense her flames, enabling her fire to cut clean through various objects. When formed into fireballs, the flames served to be rather concussive, able to firmly pulverize objects such as stone. Azula was able to generate powerful shields of swirling flames which could withstand the full force of four simultaneous elemental attacks (and a boomerang). She was even able to charge up her fire before releasing it, as was seen during her fight with Aang. Azula was also capable of fighting off multiple Kyoshi Warriors, using both firebending and hand-to-hand techniques. The outcome of this fight was not shown, but the fact that Azula, Mai, and Ty Lee infiltrated Ba Sing Se posing as the Kyoshi Warriors revealed that Azula had won. Azula later stated that Suki was her favorite prisoner, further revealing that she had won the duel against Suki.

Azula was 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 than usual. Despite her state of mind, her attacks on Zuko and Katara during her final duel proved ferocious and destructive, and she 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.

Strategy
Azula is remarkably intelligent and a tactical genius. Despite being only 14 years of age, she is arguably the most competent and dangerous planner and strategist in the entire series. She was also highly manipulative, often stringing people along without them even realizing it. She also knew how to use political instabilities to her advantage, was able to think outside of the box for unique strategies and could change her plans at the drop of a hat when she saw better solutions.

While these were displayed many times throughout the series, they were never displayed as throughly as in the second season finale, in her takeover of Ba Sing Se, a city that had withstood siege for a century.

Infiltrating the city with only Mai and Ty Lee, disguised as Kyoshi Warriors, she realized the political instability of the city and widened the scope of her original plan from just capturing the Avatar, to conquering the city. She had her friends discuss who they were so they would be heard by the Dai Li, the source of the instability. Taken to their leader, Long Feng, they both plotted a coup on the city's leadership with him placing the Dai Li under her command, both planning to betray the other.

However, she gained the Dai Li's respect through her charisma and ruthlessness and, once the coup was complete, turned them against their leader after he attempted his betrayal. She then successfully stopped her brother from changing sides by appealing to his greatest desires, and nearly succeeded in killing Aang.

Using only two non-bending friends, and her tactical brilliance, she not only succeeded where entire armies had failed for a century in conquering the city, but also took away a powerful ally for the heroes (temporarily), and put Aang out of action for a good period of time.