O.K., so she's technically a coach, but Sue Sylvester wreaks so much havoc on the students and faculty at William McKinley High School that she has to make our list. As head of the national-champion Cheerios cheerleading squad, Sylvester focuses her aggression on an unlikely rival: the New Directions glee club. Because her team fights other clubs for funding, Sylvester becomes the glee club's most ruthless bully. She's been known to throw dirt in their faces and shove them into lockers. And that's only in one episode.