The Russian Revolution killed 10 million people (Stalin later over 20 years killed 20 million more)
Vladimir Lenin brought the idea of Communism to Russia.
Originally Communism was designed to be a revolution of the industrial working class (factory workers) overthrowing their political and financial superiors. A utopia would be created where people share the wealth and the people would have the power.
This idea never came into being, but the name lived on. When faced with the opportunity for power the strong seize control. Lenin took power and instated a dictatorship. Anyone associated with the security services Cheka or the small government circle had special privileges over other citizens.
Many citizens lived in a state of fear as being called a Royalist or a counter-revolutionary by anyone could get you killed.
Lenin tried to instate the ideas of government controlled industry and farming but the results were disastrous and only produced famine and low productivity. He also promoted world revolution through radio and media outlets, with little success. After victory in Russia’s civil war Lenin died in January of 1924 leaving a power vacuum in Russia. His last wishes were to avoid having Joseph Stalin take power in Russia as he thought that Stalin was corrupt. Stalin was able to slowly destroy and kill many of his opponents so that he was in complete control of Russia by 1928. Throughout the 1930’s Stalin killed anyone who could challenge his authority including politicians, activists and generals. This is called the Great Purge. Combined with the collectivized farming policies of Stalin that produced incredible famine, somewhere around 20 million people died in Russia.
Regardless of the situation in Russia, Communism scared the rest of the world. The working classes of the world far out numbered the wealthy. If revolution came there is very little most nations could do to prevent it.