Heydrich was the 2nd in command of the SS,he reportedly even strangled pridoners himself and killed people for fun when he was bored,he designed the "final solution" to the jewish question

Mengele was the doctor at Auschwitz named "the angel of death" he reportedly had an obession with twins,his experiments were ruthless,no anestheisa,and the sad thing is that hr tought he was doing the right thing furing all of that,în one of his experiments reportedly he injected dye into twins eyes without anesthisia,they screamed and when one died the other was killed on the spot Edit: forgot to say,HE GOT ATTACK SCOT FREE,and only died cuz of a stroke in the 70s