Azula

(SHE IS OVER 18) Azula was a princess of the Fire Nation, daughter of Fire Lord Ozai and Ursa, younger sister of Zuko. She was a key adversary of Team Avatar, chasing Avatar Aang and her banished brother far across the Earth Kingdom accompanied by her then two best friends, Mai and Ty Lee. She was a also a skilled strategist who orchestrated the coup of the Earth Kingdom capital, Ba Sing Se, and halted the invasion on the Day of Black Sun. Azula harbored deep mental instabilities, believing her mother loved Zuko more than her. Raised by her father in an environment without a mother-figure, Azula had to be nothing less than perfect in her father's eyes in order to gain affection and attention from him.