Ron the Death Eater | Bulbagarden
Then again, other fandoms do this to rich characters too. Even if the character is snobbish in canon, it will be exaggerated in fanfics (for example, Rhonda from Hey Arnold is kinda stuck-up and very into fashion, but not extremely awful. Fanfics, however, often make her more like Regina George from Mean Girls).
However, alternate character interpretation can be a good thing too. Today I read a fanfic of the original Karate Kid movie that provided Johnny (the villain) with a backstory that cast him in a more positive light than he is portrayed in the movie. I was actually very impressed by the author's writing skills and choice of character development.
(NOTE: I'll let people talk about ANY fandom in this thread. It doesn't have to be just Pokemon.)