You forgot to include Mao Tse-Tung, Pol Pot and Genghis Khan in the list.
All of them are perfect candidates for 'the most evil man' title.

Along with Tomas de Torquemada, Vlad Tepes and Idi Amin.

And....
look here:

http://en.wikipedia.org/wiki/Mass_murder

I know it's hard to compare but I don't know who's more evil, political leaders who introduced terror as the instrument of political rule or individuals who commit mass murders just for the fun of it.