As Rational Poster said it.
Stalin, Mao, Idi Amin, Genghis, Pol Pot, Mohammed, Napoleon (this guy even saw his soldiers as just a mass, the bigger the mass, the bigger chance of not losing a battle) etc etc. The history has seen some really shitty people in power, but the cultural impact, making a blue print in to our souls has never been on the same level as Hitler. You can´t find a figure in the history of mankind who has had this impact. Hitler and the symbol of the Nazi cross is simply the ultimate insult to human life. And someone mentioned Stalin. Maybe if he was more of a public figure and made some more bombastic speaches and were not so shy with his own persona, maybe he would have had the same impact. But he can´t hold a candle compared to Adolf.