Noted historians and Russian policy experts admit that Stalin was not Lenins choice. Lenin was aware that rude negotiation and ruthless intention were the qualities of Stalins personality. He would have definitely blocked Stalins rise to power. However, Stalin went on take advantage of the situation that arose from Lenins death. He easily sidelined Trotsky and other senior members of the communist party. In first few years of his rule, Stalin systematically got his adversaries assassinated. Through the policy of collectivization of farms, Stalin inflicted deep scars of famine on the Russian people. Medium and large farms were forcibly acquired by the state in order form huge collective farms this led to steep drop in agricultural output.
Since, the ideals of Soviet Union prevented from any import or export, millions of people died because of starvation. Within few years of coming to power, Stalin acquired the status of a totalitarian. In 1945, George Orwell crafted a wonderful satire that depicted the greed and corruption as the driving motives behind a dictatorial regime. (Orwell, George, 1945)
USA and other allies of World War 2 soon realized that Stalin has built a fear of his personality to control and intimidate other members of the Soviet Union. Perhaps the most gruesome of his policies were to imprison millions of Russians and use them in labor camps for construction of roads and dams. Because of his policies, USSR and USA got embroiled into issues like Korea War and Vietnam War. Even though Stalin died in 1956, his policies continued to haunt the world for decades.
Had Lenin survived a few hours and passed the command to a more humane leader, the world would have been considerably more prosperous and secure for the next fifty years.
Orwell, George. Animal Farm London. 1945