The correct answer is - Joseph Stalin.
The Georgian born leader of the Soviet Union, Joseph Stalin, comes to be the cruelest of all dictators in the history if we take the statistics as measurement. During his rule millions of people had died in the USSR, some because of killing, some because of torture, some because of forced work in extreme conditions, some of starvation. Lots of people have also been forcefully moved away from their historic lands, like the Chechens for example who were almost totally destroyed as an ethnicity. Because of Stalin millions of people lost their lives, and the main reasons for that were ethnic origin, religion, different political opinion.