Among the leaders of the 20th century, arguably none shaped the course of history as much as Vladimir Lenin (1870-1942), the Communist revolutionary and political theorist who led the Bolshevik Revolution that established the Soviet Union. In addition to shaping the Marxist-Leninist political thought that steered Soviet ideology, he was the first Soviet premier until his death and set the Soviet Union on its way to becoming one of the world's two superpowers for most of the century, in addition to being the West's Cold War adversary. As it turned out, the creation of the Soviet Union came near the end of Lenin's life, as he worked so hard that he had burned himself out by his 50s, dying in 1924 after a series of strokes had completely debilitated him. Near the end of his life, he expressly stated that the regime's power should not be put in the hands of the current General Secretary of the Communist Party, Joseph Stalin.

Of course, Stalin managed to do just that, modernizing the Soviet Union at a breakneck pace on the backs of millions of poor laborers and prisoners. If Adolf Hitler had not inflicted the devastation of World War II upon Europe, it's quite likely that the West would consider Joseph Stalin (1878-1953) the 20th century's greatest tyrant. Before World War II, Stalin consolidated his position by frequently purging party leaders (most famously Leon Trotsky) and Red Army leaders, executing hundreds of thousands of people at the least.

Along with Vladimir Lenin, Trotsky led the October Bolshevik Revolution of 1917 and held crucial posts in the early Soviet governments, but after Lenin’s death Trotsky was exiled, persecuted and finally murdered at the behest of his arch-rival, Joseph Stalin.