In my honest opinion, Communism is the second sickest political ideology ever developed.
Only Nazism is worse in my mind.
Granted, the communist killed more people, but that's because communism evolved in more countries, whereas the Nazi policies last just over a decade and only within Germany and the areas they conquered early in the second World War.
Nazism is worse to me because of the racial genocide aspect of it, which is just sickening.
Communism is a close second, however.