This came from watching Bill Burr while drunk. When he says “before Hitler what did they say when somebody was like the benchmark of evil? Trumps the next Hitler.” Is there actual evidence before Hitler where people would compare other world leaders to another bad dictator? Is there more to it as well? Is it just a modern thing?
So for me personally the first name that comes to mind is Napoleon because he was seen as:
In fact, before and during WW II comparisons were made between Hitler and Napoleon, something Churchill did not approve of "I certainly deprecate any comparison between Herr Hitler and Napoleon; I do not wish to insult the dead." (1940) and "I always hate to compare Napoleon with Hitler, as it seems an insult to the great Emperor and warrior to connect him in any way with a squalid caucus boss and butcher." (1944) You have to remember at this time Hitler had seemingly pulled a floundering Germany out of an economic depression, re-armed her, and against all odds had erased the humiliating failure of WW I. Standing alone and isolated, facing off against the seaming military "genius" of Hitler (helped in no small part by the Nazi propaganda apparatus) Britain must have felt like it was 1812 all over again. In Russia Napoleon's invasion was known as The Patriotic War of 1812 and comparisons were made between the old and the new and improved "Great Patriotic War", including an unflattering comparison of Hitler too Napoleon.
Now with that being said I think something that matters most is context. Meaning it largely depends on who, where, and when you are. For the British in WW II Napoleon made an apt historical analogue because the memory of the threat he posed and crimes he committed was shared among Englishmen. Before WW II other historical figures were used to help explain Hitler: Henry VIII, Attila, Genghis Khan. In Germany, before his rise to power Hitler was himself compared by some in the press to Maximilian Robespierre. (Rosenfeld 2018) For Americans a reviled figure who stood as a historical "boogeyman" would likely have been George III. But as you and Bill Burr were getting at, Hitler has seemingly displaced all other historical figures to become the universally reviled "benchmark of evil" (at least in the Western Hemisphere).
Sources:
Gavriel Rosenfeld, "Who Was “Hitler” Before Hitler? Historical Analogies and the Struggle to Understand Nazism, 1930–1945". Central European History. 2018. link to open access PDF
winstonchurchill.org
