Answer:
Correct answer is Josef Stalin .
Step-by-step explanation:
Josef Stain is correct answer because during his reign millions of Soviets were killed, prosecuted and sent to Gulags because they opposed his policy. More Soviets died from his hand that from the hands of enemies.
Nikita Khrushchev was Stalin's successor who reign during the period of Cold war. In comparison to Stalin he was not such a cruel leader.
Lenin is not correct as he was at the head of the country during the period of Civil war in Russia and political changes that led to creation of Soviet Union.
Yeltsin is not correct as it refers to first president of Russia after the dissolution of Soviet Union that wasn't that influential.