The Face of Evil: Nazis, Communists and ISIS

 "The only thing necessary for the triumph of evil is for good men to do nothing."

Hitler: The Rise of Evil

This is a BBC2 documentary from 2003 and probably one of the best on Stalin. The archive footage is very good and it draws upon some excellent evidence from close witnesses, including Stalin's own family.

Chairman Mao : Documentary on the Secrets of Mao Zedong (Full Documentary).

And today ISIS