My favorite cartoon network villains are: Mandark (Dexter's Laboratory), Red Guy (Cow and Chicken), Mojo Jojo, HIM, Fuzzy Lumpkins, Gangreen Gang, Amoeba Boys, Sedusa (Powerpuff Girls), Katz (Courage the cowardly dog), Aku (Samurai Jack) General Skarr and Mandy (Billy and Mandy and Evil Con Carne), Father (Kids Next Door), Scoutmaster Lumpus (Camp Lazlo, even though he's an antagonist), Vilgax (Ben 10), Benson (Regular Show), and many others.