The German Nacional Socialist Worker's Party, known as the "Nazi Party", came to be also as opposition to the idea of Marxism. Hitler's socialism, according to himself, was a different one; a nationalist one. So socialists, Marxist socialists, that is, and communists as well were also hunted down.
The nazi theorized that all non-Aryan populations were inferior beings. The Slavs, Poles and Russians were the worst one, but Scandinavians, for example, were among the best.
It is known that many Slavs, Poles, Gypsies, and handicapped people died by the hands of the Nazi Party. The last one most likely to prevent bad genetics to get mixed within what they considered to be the superior race. They also went for Jehovah's witnesses and even homosexuals.