21. Josef Mengele
His nickname “Angel of Death” speaks a lot, and he was one of the main people responsible for Auschwitz concentration camps. Besides sending over 400,000 people to die in the gas chambers, he was also quite familiar for experimenting on people, especially twins. He would sew them together, try to change their sex, their eye color, and out of 3,000 of them, only 200 survived, and it is not surprising that he is on the list of most evil people in history.
