Heinrich Himmler, the architect of the holocaust and final solution, and considered to be the biggest mass murderer ever, by some (although it’s really Josef Stalin). The holocaust would not have happened if not for this man. He tried to breed a master race of Nordic appearance, the Aryan race. Himmler was captured after the war. He committed suicide by swallowing a cyanide capsule he had bit upon.
Heinrich Himmler followed by Reinhard Heydrich. Though Hitler was, and remains, the public face of the Holocaust, these two men were the will and organization behind it. As mentor and protege, they were responsible for the systematic murder of millions of human beings. Heydrich, as cold and arrogant as only a true Nazi could be, was assassinated in 1942. Himmler committed suicide in British custody in 1945 after turning traitor to the Reich and being refused pardon by the Allied powers.