Azula

The main antagonist from the TV series Avatar: The Last Airbender. Azula is the princess of the Fire Nation and Zuko's sister. She is cunning, malicious and a perfectionist. She is a Firebending prodigy, thus making her Fire Lord Ozai's favorite child. She was sent on a mission by her father to capture and bring Zuko and Iroh back to the Fire Nation to be imprisoned. She had a group of her and two 'friends', Mai and Ty Lee. In Book Three of Avatar, Mai and Ty Lee betrayed Azula, because they never really liked her. In Sozin's Comet Part 1: The Phoenix King, Azula is told by her father that she will become Fire Lord. This sparks Azula's insanity. After this, she starts banishing most of her servants, cuts off her hair, hallucinates her mother and letting herself get captured by Katara. She doesn't become Fire Lord, instead Zuko does. She currently resides in a metal asylum somewhere in the Fire Nation, where she is constantly supervised.