The USSR didn't "do repression and violence to speed up Communism," they had a successful revolution and established Socialism. By all accounts it was quite successful overall, but we can learn from where they erred and adapt for the future.

The only ones who believe the Soviet Union wasn't Socialist are generally Western Trots or liberals/Anarchists who already don't want the form of society Marxists want, which is a government that publicly owns its large and key industries and gradually folds in the new firms that grow to that level until the entire economy is publicly owned.