Also "worse" than the Nazis going by death toll. We just don't learn about the genocide and political excisions that occurred under Stalin alone because we were war buddies. Nazis had darker motivations, sure, but its a different brand of evil to execute his own people. Going by sheer death toll, 20 to 40 million are believed to have been executed
British Empire was much worse, killing 30 million Indians in the late 19th century, and possible 1 billion or more indigenous peoples of India and the Americas throughout its 400 year rule.