I'm God fanfiction
This is when the writer takes a story and messes it up just because they think they're better than the original. The characters are still around, but they're total garbage and only exist to make the writer look good.
A Naruto fanfic where Orochimaru is a shy, soft-spoken boy who cries when he's sad.
A SoulEater fanfic where Maka is a prissy, overly dramatic girl who yells at everyone.
A Sonic fanfic where Sonic is a loud, obnoxious, and completely useless jerk.