The Dark Doctors Michael Jayston, Toby Jones, John Hurt...? (1986, 2010, 2013)
Twice the Doctor has confronted future versions of himself with all the goodness removed. One of those was the Valeyard, an incarnation somewhere between the 12th and 13th Doctor that had all his darker impulses. He traveled back in time and manipulated the Matrix so as to make the Doctor look guilty of many horrible crimes. In the process he corrupted the path of Time Lord justice and managed to get one of the Doctor's companions killed...or not. It depends on what ending you prefer. Then in 2010, we got the Dream Lord, another distillation of the Doctor's darker desires. We don't know where, if at all, he fits into the Doctor's timeline. But he was an interesting character, and one we will hopefully see again. Lastly we have the Hurt Doctor. We don't yet know who or what he is. The current rumor is that we can view him as the Eighth-and-a-half Doctor; someone between Eight and Nine who does something horrible during the Time War to make him unworthy of being called the Doctor. Is he a dark and evil force? Is he simply a version of the Doctor who did what must be done and can't live with it? Time will tell. It always does.