Azula, from Avatar: the Last Airbender.
Not only will she wipe the floor with you, burn you alive, and leave you alive to feel the agony, but she will be mind raping you every step of the way. Smiling the entire time. The only way to escape the living hell that your life will become... is to kill yourself.
Then she wins her sick little game, and forgets you by the next morning. She forgets, because your pain didn't really even matter to her. It's just the state she prefers to see people in.... and Azula always gets what she wants.
Azula scares the living daylights out of me. Is it obvious?