Arguing terminology is not really that helpful here, nazis called themselves socialists. And very few countries with “democratic republic of” in their name are democratic republics.

The terms Socialism and Communism have been used interchangeably since the beginning. This move to split socialism off is both a move by some within the movement to be more palatable to liberals and a move by opposition from without to further factionalize the movement. However, many people use the terms interchangeably or use communism to differentiate themselves from capitalist liberals claiming to be socialists.

Specific subsets of communism/socialism like Marxism, Leninism, Stalinism, Maoism, vanguard theory and various other implementations of communism are violent, should be criticized and learned from.

All this is to say plenty of people claiming to be communists do not want widespread suffering or genocide. They may be willing to use force to implement their ideas, but so are the adherents of nearly every other ideology.

Nazis always want racial segregation and the of Jews. Communists want equity. Nazis want superiority.

What you are focused on is Vanguard Communism which proposes that because the workers are not yet educated enough to understand that communism is better for them, a group of communists should make a totalitarian government. That totalitarian government will then shepherd the country to total communism.

History shows that this form of communism generally falls to corruption and they never get to full on communism. The proponents of this view always blame outside influences (like the west), while conveniently ignoring that power corrupts everyone.

Cuba is often shown as an example of successful vanguard communism. However it still hasn’t fully divested the communist party of its totalitarian power, and a lot of migrants move to Florida. So, it doesn’t really meet the criteria in my eyes.