There is a popular argument against communism that accuses Soviet communists of murdering more people than the Nazis. This argument refers to the deaths that resulted from Joseph Stalin's orders. However, the argument fails when you try to find out which communists performed or agreed to Stalin's murderous purges. Because nearly all of the founding communists assumed to have been complicit in these mass murders were themselves murdered by Stalin during the purges.
If the communists that led the communist revolution were mostly murdered by Stalin, how can communists be held responsible for Stalin's crimes? I don't believe that the people who helped Stalin murder the original members of the Bolshevik Party Central Committee can properly be described as communists. They were wiping out communists, under Stalin's orders. Stalin posed as a communist but was deadly to communism.
Of the 21 members of the 1917 Bolshevik Party Central Committee, apart from Stalin himself and Trotsky, who was to be murdered in 1940 under Stalin's orders, only two others were still alive or not imprisoned by 1938. Those two were Alexandra Kollontai, who was serving as an ambassador to Sweden, at the time of the 'show-trials' of 1937. These show trials were to provide a legal justification for the murder of anyone whom Stalin considered to be a threat to his rule. Matvei Muranov, who had supported Stalin's usurpation of power in the 1920's, was the only -other survivor. Stalin's purges happened at every level of society and within the army.
If we look at this evidence, we find that the claim that communists, whether the 1917 Russian Bolshevik Party or their allies in Germany, killed more people than the Nazis that they fought against, is a baseless smear against the very people who might have prevented the slaughter of 70 million people between 1931 and 1945, had they lived.
Much of this has been forgotten due to the long-term corruption of the Trotskyist movement. People claiming to be Trotskyists have themselves become corrupted to the point where, ironically, many are now rioting in support of yet another attempted Maidan-style coup against President Donald Trump and in support of Hillary Clinton.
Not to be confused with Stalin's purges, were the executions carried out on the orders of those in command of the Red Army, during the 1917-1921 civil war, in which the Soviet Republic was fighting for its existence against the internal counter-revolutionaries, who were backed by about 13 foreign armies. Some historians opposed to the Russian Revolution use this to claim that Stalin's brutality was characteristic of communism from its inception, but this was civil war and the scale was not comparable to that of Stalin's purges.
 Historians who support the Russian Revolution tend to understand Stalin as having begun as a sincere communist but to have become corrupted by the privileges of power.