@ Virginia:
Yes, certainly I would rank the Soviets in the top 10.
Actually, they were a continuation of the Russian empire. When the latter collapsed after WW1, what was the first thing the Communists did? They reconquered all the parts of the empire that had broken away, and very brutally. Ukraine, Armenia, Azerbaijan, Byelorussia, the Baltic states, etc. And of course, after WW2, they took over Eastern Europe. And while the communist revolution in China did not make China a satellite of the Soviets, it was another step in the declared intention of world domination by communism.