Which person was most important for the formation of the soviet union?

Vladimir Lenin was the most important person for the "formation of the Soviet Union".

Explanation:

Vladimir Lenin was the supreme leader of the Bolsheviks that brought down the "provisional Russian government" in October 1917. A treaty was signed in 1922 which led to the formation of the Soviet Union. The proposition of this treaty was a brainchild of Vladimir Lenin. Vladimir Lenin persuaded convince the Ukrainian, the Transcaucasian, the Russian and the Byelorussian republics to sign the treaty of the formation of the Soviet Union.