That question is too politicized. No one will give you the true number. Stalin's purges is a good example. Various "researches" will give you numbers in the range starting with something about a million (for the whole time of his rule) to over 60mln. For anti-stalinists the trick is to include all jailed people, not just the political ones, famine victims, the civil war victims, the ww2 victims and so on and so forth. For the stalinists the trick works the same way, just in the opposite direction.

What bothers me when people ask questions like that. Does it really matter? If the number of victims is less than a million, then Stalin is a good guy? And if it is 1mln+1 than he is a murderous monster? How is it supposed to work, this kind of arithmetic?

According to Victor Zemskov:

799 455 persons were executed in the USSR from 1921 till 1953 for counter-revolutionary crimes and other state crimes.

Search Google "В.Н.Земсков. О масштабах политических репрессий в СССР."

Who understand Russian can read this book "Victor Zemskov. Stalin and people. Why there was no revolt"

ISBN: 978-5-4438-0677-8

No a great number..However millions died at the

guns of Communists..

, Mass killings occurred under some Communist regimes during the twentieth century with an estimated death toll numbering between 85 and 100 million. And it started right after the Revolution, even before Stalin era.

http://en.wikipedia.org/wiki/Mass_killin...

At least 20 million.

No one really knows, but it's estimated Stalin's regime alone killed many millions:

http://en.wikipedia.org/wiki/Joseph_Stal...