Yeah, direct democracy has problems. John Locke solved most of those with the idea that the Founders/Framers eventually put into place: a constitutional republic.
Communism as a governing philosophy, much like socialism, is dependent on contradictions that tend to lead to authoritarianism. (Authoritarianism on a mass scale is generally colloquially known as fascism.)
The 80 million dead was under, mostly, Stalin and Mao. But you can also throw in Che, Castro, Pol Pot, and a few others.