Talk-Polywell.org

Found this handy chart.

For perspective, what are the relative populations of the nations they ruled?

It is a rather judgmental interpretation of history, I think. Especially Mao. OK, so he introduced ignorant socialist reforms that lead to the unnecessary starvation of many people, but this is quite different to an intentional policy of execution.

There is also a difference between actions where persecution was allowed [by others], or some action [to stop it] was omitted, to signing off death warrants, to deaths caused in the prosecution of a war.

One might argue, for example, that the omission of America entering WW2 at an early stage lead to the deaths of millions. We're in a moral morass here, with this chart, but I'd not put Mao at the top. He was a victim of socialism in the way that it turns its supporters into gibbering anti-intellectuals who think you can make high grade construction steel by melting down old pans in your back yard. This is stupidity, not brutality. Not that I condone the brutality of Mao's system, by any means, but I do not believe direct killings hit 'millions'. Stalin is waaay ahead in willfully commissioned brutality. He makes the others look like part-time amateurs.