Nazis killed an estimated 6 million Jews as well as 3.3 million Soviet POWs, 1.8 million ethnic Poles, 310,000 Serbs, 250-500,000 Roma, 250,000 people with disabilities and many Catholic leaders because of their hope to de-Christianize Europe.
Holocaust
Nazi genocide of Jews and others; ~6M Jews, plus Roma, disabled, POWs.

Former inmate of German concentration camps who later became a citizen of Israel. Source: Eisenhower Library.