Final answer:
Josef Mengele was nicknamed the "Angel of Death" due to his horrific medical experiments on prisoners in Auschwitz concentration camp.
Step-by-step explanation:
Josef Mengele was nicknamed the "Angel of Death" because of his role in conducting horrific medical experiments on prisoners in Auschwitz concentration camp during World War II. He was particularly interested in twins and carried out painful and often fatal experiments on them without their consent or any regard for their well-being.
Mengele performed numerous painful and unnecessary procedures on his subjects without their consent or anesthesia. These included amputations, injections of harmful substances, and the removal of organs for study. His cruel and inhumane actions earned him the nickname "Angel of Death" and he is remembered as one of the most notorious war criminals of the Holocaust.