If you are comparing who controlled the largest number of slaves between George Washington and the two major communist powers of the 20th century, there is no competition—the communist regimes win hands down.
In general, the populations of Russia and China were so terrified and so submissive to the Communist Party that they often did things they knew were irrational and would cause suffering later. During the Great Leap Forward, for example, peasants were ordered to give up their tools, woks, and cooking cleavers to be melted down in backyard furnaces so Mao could meet his goal of making China the world’s leading iron producer.
So they complied, and the very tools they needed to make a living were turned into heaps of worthless pig iron. They knew what they were doing—they were surrendering the tools essential for survival—but they did it anyway, and many later suffered starvations as a result.