Sideshow Bob
Robert Underdunk Terwilliger Jr, better known as Sideshow Bob, is one of the main antagonists (and sometimes an anti-hero) of the animated TV series The Simpsons. He is Bart Simpson's archenemy.  Sideshow Bob used to be Krusty's sidekick and best friend and co-star of the Krusty the Clown Show, but soon he was so tired of being humiliated by Krusty and wanted him off TV.  He was originally Krusty the Clown's sidekick until he framed Krusty for robbing the Kwik-E-Mart, however he was foiled by Bart Simpson who exposed Bob's scheme. And ever since then Bob has vowed to kill Bart, though on some occasions he has also gone after Krusty.