Proven by who? I'll need more than an anonymous internet person to take it seriously. A book or paper by a professional historian would be credible.
Besides, even if the stats are exaggerated by factor of 10, communism still winds up being terrible.
Simple question: do you attribute all preventable or violent deaths under capitalism to the ideology of capitalism? If yes you probably have over billions of deaths since the ~1600s.
Simple answer: I would count violent purges and death camps, mass executions, deliberate impositions of famine, deaths due to mass confiscation of property, gulag deaths, etc. Those are active killings of people.