Cartoon villains turning over a new leaf

Greetings!   I discovered Megamind on DVD in August and have been more or less obsessed with it ever since.   This is a really wonderful site; I am really enjoying reading the posts and stories.   
  Anyway, I was pondering the rarity of fictional villains from any genre who turn their lives around.   But there have been a few in cartoons that I know of.   For example, Gru from Despicable Me.   Also, there is a character from the TV cartoon series Avatar the Last Airbender named Prince Zuko.   This show aired on Nickelodeon a few years ago.   (If you haven't seen it, I highly recommend it.   Check it out from the library.)   The Avatar's name is Aang, and it his destiny to realize his full elemantal powers and bring balance to the world.  Unfortunately, Prince Zuko believes that it is his destiny to capture the Avatar.   The arc of Zuko's story is as important as Aang's, which, I think, made for great drama.   It takes a long time, but Zuko eventually comes to realize that... maybe he got his destiny wrong.   
  In the cartoon Ben 10, I believe that one of Ben's friends was once on the wrong side of the law, but then he joins Ben on his adventures.   I'm afraid I haven't watched this series too much, so I don't know what his name is.
  Does anyone know of any other cartoon villains who turn over a new leaf?