they r all as bad as they get to be honest regardless of the number of people they had killed, in my opinion there are more worse crimes committed by dictators than killing there people in cold blood ( not saying its simple off course not human life is never simple and killing is the lowest thing a human being can do to another human being), like destroying the identity of a nation, biochemical bombings on civilians, destruction of education systems to ensure total control, bribes, and financial corruption that leads to a tiny percentage of the people having the means to run the country with out having to answer to any one, also using people's emotions to get behind any efforts of getting involved in a war for personal gains ( also not necessairly using war, some dictators use religion to herd people, due to the wrong mis-understanding of there religion and piss poor education system which is designed to make the people worship the dictator and that god is in the sky and he is down here!), and finally getting yr foreign policy messed up and jumbled to the degree the people who historically, culturally, and religiously programmed to be yr allies become yr enemies and yr enemies become yr strongest allies.
if they use the above mentioned categorey i think the arab world, the balkans, persia, etc etc will have hot contenders to compete with the above mentioned dictators who have there own people's blood on there hands.