Edit: Why downvotes? Idea of communism does not propose violence, Nazis and ISIS on the other hand do.
...or Maoism "struggle sessions" which resulted in 2 million deaths [1]
...or just read about mass killings in communist regimes[2]. Clearly communist governments have mass killed a lot of people.
[0] https://en.wikipedia.org/wiki/Red_Terror
[1] https://en.wikipedia.org/wiki/Struggle_session
[2] https://en.wikipedia.org/wiki/Mass_killings_under_Communist_...