And here's why.

Hitler was evil no doubt about that but he was also a mentally ill asexual, thus excluding him from pure evil.
Sadaam is a small time megalomaniac (yes I realize its a paradox) who never invaded a country without American help.(Kuwait was Iraq till the British went in and made a balls of it. Yes he did evil to his own people but nothing
like supplying cheap smack to black ares to curb the Panther movement
Jack the Ripper was your everyday psycho killer weather you belive the Walter Sickert theory or not.
Mao Tsetung was just a communist revolting against regime,Ok he replaced in with another but he was honest about it at least. And besides I'm not communist but I'm heartily sick of people bashing the theory of it which makes sense at least

George Bush introduced the Patriot act. It negates the thing that makes America great. The Constitution is rendered null and void by this act. It suspends peoples constitutional rights during times of national emergency. The U.S. has been in a state of emergency since 9/11, be it yellow alert or whatever.
I don't think he the most evil ever but if that list he certainly take that dishonour.
Thats the way I see it.