Question

Who introduced communism to the former Soviet Union?

Answer 1

No one? Communism is still around in the former Soviet Union, particularly Russia, it just doesn't have the power it used to enjoy during the Cold War. A communist party continues to vie for seats in the government every election cycle over there.

On the other hand, if you're asking for who first brought it over to Russia and formed the Soviet Union, that'd be Vladimir Lenin and his Bolsheviks who were responsible for its founding.