My favorite villain in the Simpsons has to be Sideshow Bob. For those who do not know Sideshow Bob used to be the assistant of Krusty that went through a lot of abuse. He wanted to get revenge by framing his employer but Bart was able to foil his plan. He is my favorite villain because he does not want to stop. He is persevering although he is using his perseverance in a bad way which is to kill Bart Simpson eventually.
If he would use his persevering nature for a lot of other things, he would be able to change his whole life. I believe that a lot of people go through change but people will always get a choice if they want to change for the worse or for the better.