It was more of a struggle between the Soviet Union and China.
Communism
Stalin
Tens of thousands of pro-communism protesters were killed by the military Dictatorship in power
Communism
The 1917 October Revolution in Russia was the first time that Communism came into power.
Depending on your political position, you could argue that the creation of communism brought its demise. Or, to be kinder to communism, the people promoting communism were using "communism" as an excuse to grab power. So it was just a dictatorship running its course.
it is that they are finish
What? Communism has never been developed in a country before
the people rule and hold sovereign power
Power, especially absolute or unchecked power, corrupts all forms of government, because all governments are run by human beings, who are inherently flawed and will naturally try to arrogate more power to themselves, even if they believe they are serving the people and the greater good. Communism, either as an economic model or a system of government, is inherently flawed in ways that have little to do with the exercise of power.
A centrally planned economy with all economic and political power resting in the hands of the central government is known as communism. Karl Marx developed communism into a scientific theory.
Qustion is mal-phrased: a a communist can be the same as an autocrat (false, because not all communists can be autocrats), but the interesting question is whether communism is always an autocracy. This is for the experts to answer.