As the title asks, was there ever a leader before Hitler that was used in extreme comparisons? Would one call an aggressive monarch "literally Napoleon"?
You should check out these threads:
http://www.reddit.com/r/AskHistorians/comments/zv1p7/who_was_considered_the_most_evil_person_in/ http://www.reddit.com/r/AskHistorians/comments/1c7ckr/