They commonly break laws of canon and generally warp the story or Roleplay to be as they see it, regardless of anyone else. Usually, said canon manipulation is used as a way to a) get to the romantic interest quickly, b) kill off the character/s they don't like, or c) rewrite an episode or season or film or book so that the ending suits them. The effort fails 98.7% of the time. Godplayers will gain new powers randomly, warp canon to the point that it is unrecognizable, and sometimes even declare themselves completely immortal.
In Roleplay, someone who uses these strategies will take control of others' characters, not just creating canon breaks but severely annoying the other players.