The political system that you are calling 'communism' has never really worked on a national scale.
The few countries that claim/claimed to be communist were nothing of the sort - just another form of dictatorship.
The name Nazi came from the first two syllables of the National Socialist party - German speakers would pronounce it that way. So, they were Socialist?
The Soviet Union, led by Lenin and Stalin et. al., were also 'Socialist' - it's the second 'S' in USSR. Again, more of a dictatorship, driving the normal people into poverty to enrich a few.
The People's Republic of China - communism? In their version everyone gets a job, but only a select few get any wealth. To some extent that has changed and they're now more capitalist than anyone, but still persecuting minorities.
Venezuela - definitely claimed to be Communist, but I don't think they shared out the oil wealth very equally.
Cuba - they're very communist: everyone is equally poor, except the people running the place. Same goes for North Korea.
Which communist government has actually killed more people than Hitler's Final Solution?
I don't think communism has killed many people at all, but fascism pretending to be communism has done quite a lot of damage to the communist ideology.