The character who is obsessed with getting revenge on Bart Simpson in "The Simpsons" is Sideshow Bob, also known as Robert Underdunk Terwilliger. Sideshow Bob is a recurring character on the show, and he is known for his distinctive voice and large feet. He is a former sidekick of Krusty the Clown, and his main goal is to exact revenge on Bart for constantly foiling his plans. Sideshow Bob often devises elaborate schemes to harm or outwit Bart, but his plans are typically thwarted by Bart and his family. Despite his criminal nature, Sideshow Bob remains one of the most memorable and beloved characters on "The Simpsons."