From that link.
http://popten.net/2010/05/top-ten-most-evil-dictators-of-all-time-in-order-of-kill-count/
Yeah,they liberated close to 100 million from life.
Gee! monster numbers 9, 8, 7, 3, 2, and 1 were some form of Socialist. I think I discern a pattern. Extreme nationalism, racism, and tribalism don't come off very well, either, accounting for numbers 10, 6, 5, and 3 (Hitler was both a nationalist-racist and a non-Marxian Socialist).
The horrible colonialists? "Just" the one, number 4.
The Sudanese (Arabs) genocide against southern (= black) Sudanese (most of whom became South Sudanese) and the massacres of Tutsis by Hutus must have missed being on the list by not fitting the strongman dictator paradigm. If added to the list based on number killed only, they would fall under the aegis of nationalism, racism, and tribalism.
One other factor is missing from the list of 10 ... the
R word. But religion was (and is?) a factor in the Sudanese genocide. Along with the racial factor, the Sudanese Arab killers-enslavers were Muslims, and most of their south Sudanese victims were Christians and Animists. Militant atheists love to blame religion for the world's wars and murderous oppressions, yet only one of the worst 12 of the late 19th and the 20th had religion of any sort as a significant cause (Muslims like ISIS and the Talibanders, and to a lesser degree, Hindus and Buddhists, are working on that, though). Unless one includes atheism as a religion, and then the atheism of Stalin, Mao, et al becomes pertinent.