"Gulpin' gargoyles, Harry, people are still scared. Blimey, this is difficult. See, there was this wizard who went... bad. As bad as you could go. Worse. Worse than worse. His name was... Voldemort. Don' make me say it again. Anyway, this -- this wizard, about twenty years ago now, started lookin' fer followers. Got 'em, too -- some were afraid, some just wanted a bit o' his power, 'cause he was gettin' himself power, all right. Dark days, Harry. Didn't know who ter trust, didn't dare get friendly with strange wizards or witches... terrible things happened. He was takin' over. 'Course, some stood up to him -- an' he killed 'em. Horribly."
-- Rubeus Hagrid (PS4)
Throughout history, some wizards have attempted to dominate and destroy. They have used Dark Magic but also played off the fears and prejudices of the wizarding population. Some famous Dark Wizards have included:
Herpo the Foul