You should look at the FAQ which discusses this.

It varied from place to place. One country's evil invader may be another country's conquering hero, after all. For example, Napoleon was a bad guy to the British, but a hero to the French. Also, you should be aware that Godwin's Law is mostly a western thing, meaning Hitler hasn't completely transcended symbols of evil being localized. People in China hate Japan's World War II leaders instead of Germany's. After all, the Nazis never affected China, but Imperial Japan sure did.

Prior to the Nazis, the most universal symbols of evil in the western world were biblical figures, such as Judas, Pontius Pilate, and the Pharaoh from Exodus. In Common Sense, Thomas Paine compared George III to the Pharaoh. Pharaoh comparison also came up during the American Civil War, when Confederate soldiers referred to Lincoln as "a modern Pharaoh" (rather ironic considering they were the ones fighting for slavery).

During the 19th century, European and American conservatives regarded the French Revolution as the epitome of evil, particularly due to its campaign of de-Christianization, and they were happy to bring up comparisons to the French Revolution for politicians they thought were too populist. This is probably best comparable to modern-day conservatives invoking the Soviet Union.