Azula

Azula is a major antagonist in the cartoon series Avatar: The Last Airbender. 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 bother 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.

Powers and Abilities
Azula is a master firebender who can shoot lightning at will. The fire she bends is blue, unlike other firebenders. It is implied that this is due to her great raw talent, hinging on the fact that fire appears blue when it is extremely hot or fueled by gas, but it is never explicitly discussed in the series. She is a skilled manipulator as well, and she seems to be able to see whether people are truthful or not, while being an excellent liar herself as Toph could not sense if she was telling the truth even though she was telling an obvious lie. She appears to take a sadistic pleasure in bending the truth to suit her purpose, which often comes in useful in battle. She is also a master strategist and appears to be very knowledgeable overall.