Homes, you are clearly reading the wrong fic, lol. Check out dark!Harry. I'm utterly loathe to recommend the darklordpotter forum (rampant misogyny, lolwhut), but they do have a variety of otherwise truly excellent writers who do exactly that.
They totally suffer from a couple cliches (evil Dumbledore or Weasleys, sometimes), but the quality is otherwise sterling. Here's their fanfic database (http://www.patronuscharm.net/)