Since using a positivist Communist philosophy to justify totalitarian rule is pretty much the same as justifying that rule by Divine Right, we might as well list the strongmen of the Soviet Union in this node. Although paramount power passed through various offices during the Soviet Union's existence, the top man was usually "General Secretary of the Communist Party of the Soviet Union". On December 25, 1991, Mikhail Gorbachev resigned as General Secretary and President, and the Soviet Union ceased to exist.  Power devolved onto the (somewhat) democratically elected presidents of the Russian Federation.

Thanks to for the patronymics and dates, and the knowledge about Bulganin (I had thought he had been General Secretary for a while).