"You, sir, are worse than Hitler." It is said that any argument - particularly an online argument - will eventually end when one person plays the Hitler card. Also known as the Nazi card, Godwin's Law of Nazi Analogies, and Reductio ad Hitlerium, the tactic is often used to derail an argument when one person knows that they have already lost. Invoking a ruthless dictator, responsible for the deaths of millions, is generally accepted as a sign that you've run out of better, more coherent, arguments. This is generally the point at which a previously heated, if logical, discussion will devolve into name-calling and profanity. Linking an idea with Hitler or Nazism has become a common means of creating a sense of guilt by association. It only works, really, because Hitler has become the benchmark against which all evil has been measured since the Second World War. But there are many criminals, most of them the rulers of countries and or the leaders of organisations, who have committed crimes that are on a par with Hitler's. There are some which are arguably worse. We've rounded up a list of of the worst crimes in history and the men who perpetrated them. So the next time someone online compares you to Hitler, you'll be prepared to one up them with the likes of Stalin, Caligula, and Ghengis Khan.