1. Josef Stalin2. Adolf Hitler3. Vlad the Impaler4. Attila the Hun5. Pol Pot6. Heinrich Himmler7. Torquemada8. Josef Mengele9. Lavrenti Beria 10. Ivan the Terrible11. Osama Bin Ladin12. Adolf Eichman13. Slobodan Milosevic14. Pablo Escobar15. Idi Amin16. Ho Chi Minh17. Saddam Hussein18. Papa Doc Duvalier19. Caligula20. NeroWell, I'm glad you got the first two right. I have always ranked Stalin as slightly worse than Hitler not because of body count, but because, as Hannah Ahrendt has noted, Hitlers main crimes were against outsiders to the state, whereas Stalins main crimes were against members of the state itself. If you were a good aryan citizen of Nazi Germany, you really had nothing to fear from the government so long as you did not challenge it; in fact, prior to 1943 your life was a pretty good one, far better than it had been under Weimar. If you were a good Communist citizen of the Soviet Union in the 1930's, your life was constant fear. Nothing would protect you; no past or current loyalties, no matter how high up you or your friends were, nothing. So far as the rest of the list goes, I'm still not sure that men like Eichmann, Beria, Himmler, and Mengele deserve greater consideration than heads of state. This is a fascinating and deep question, and I can see many sides to it. I certainly don't want to dismiss these four with the idea that they were carrying out orders- that was the typical defense at Nuremberg. But on the other hand, these guys were not the instigators. It seems to me that despite the difference in body count, a guy like Idi Amin who instigates murder should be given greater consideration than a guy like Himmler who carries it out.