Misa Amane from Death note
She came off as an immature and clueless child thinking that everything revolves around her. She's stupid, immature, childish, clueless and deluded. Light can easily manipulate her like a chess piece. Don't get me wrong, I wouldn't mind if she had entered the story as a useful character, but her immaturity and lack of intelligence make her as a nothing more than a naive child in a game of adults.
