Stalin was without doubt one of the most ruthless world leaders of the 20th Century, responsible for millions upon millions of deaths. The exact number of deaths that can be attributed to Stalin is subject to a great deal of debate, often acrimonious, between historians.
Before the collapse of the Soviet Union led to the opening of state archives to researchers, estimates of the number of people killed under Stalin’s leadership varied dramatically, from 3 million at the lowest end, to around 60 million at the top end. Post-Soviet research has shown that the number of deaths is probably around 20 million – still a horrific number. The records are not particularly accurate in many ways, though, and although a rough consensus seems to be emerging that 20 million deaths is a reasonably accurate figure, the topic is still subject to much debate.
The number of deaths in the Soviet Union that were explicitly ordered by someone – in other words, the number of executions – is actually relatively low at around 1.5 million. The majority of the deaths were caused by neglect or repressive policies – for example, around five million people are thought to have died in the Soviet gulags, almost two million people are believed to have died while being deported, and approximately one million German civilians and Prisoners of War are believed to have perished while under Soviet guard.
Much debate is also focused on whether the victims of famines in the Soviet Union – most notably the 1932-1933 famine, which resulted in the deaths of between 6 and 8 million people – should be counted as victims of Stalin. The famines were often caused by callous Stalinist policies such as forced collectivisation, that showed utter disregard for individual life, though, so if the neglect argument can be used in respect of Gulags and deportations, I can’t see a strong argument for excluding the victims of famine.
Stalin doesn’t hold the distinction of being the most genocidal leader of the 20th century. In absolute terms, Mao Zedong of China is thought to be responsible for the deaths of over 40 million Chinese (admittedly from a much larger initial population base). Again, most of these deaths are attributable to famine, and political decisions such as the Great Leap Forward. Adolf Hitler, of Germany, is probably responsible for between 15 and 17 million death but, in contrast to Stalin and Mao, most of these were systematically exterminated.