Joseph Vissarionovich Jughashvili, more commonly known by his pseudonym Josef Stalin was the leader of the Soviet Union from 1928 until his death in 1953. During his life, he was responsible for the deaths of an estimated 8 million people because of his harsh collectivisation policies pursued throughout the 1930s.
Life and Death
Stalin died on March 5, 1953, after apparently suffering a stroke on 1st March.
The extent to which Stalin had created a terror state can be seen in him not being discovered until 10:00 PM on 1st March, as his guards were under orders not to disturb him. He hadn't emerged from his room since he went into it the previous night and his guards were too scared to enter his chamber without permission, they had to receive authorisation from the Politburo instead. It took a long time before anyone felt able to call a doctor, Stalin had sent the best doctors to prison. Eventually, doctors saw Stalin and were pessimistic, the doctors in prison who had previously treated Stalin were consulted, (not released) and agreed things were bad. Stalin hung on for a few days and died on the 5th of March. It's unknown if an earlier intervention could have saved Stalin, it's also not certain if Stalin died of a stroke or was poisoned.  
In the Communist Party
He rose through the Communist Party of the Soviet Union to become General Secretary in 1922. Over the course of the 1920s, as he continued his rise, he made his title synonymous with "supreme leader."
As the 1920s progressed and the 1930s rolled around, Stalin began to commence purges of his Party, the Army and the People of Russia. As the 1930s continued and the purges became more violent and the scale of them grew, Stalin began to show more and more symptoms of paranoia, as he purged his entire Party, including all his old comrades from the revolutionary days.
Stalinism, Communism, Socialism
When Right-wing scaremongers (see Sarah Palin) and others claim moderate left-wing politicians or policies are "socialist" or "communist" they mean "Stalinist" but either don't know or pretend they don't know there's a massive difference between the three. Social Democracy has made Scandinavian countries among the Happiest countries in the world and they're not far left or Stalinist.
Stalin is known by the history as a person who imprisoned and executed large numbers of people, with different sources claiming different numbers -- with different accounts of exactly who is considered "repressed".
The best known official report on "counter-revolutionary crimes" was in a note directed to Nikita Sergeevich Khrushchev in 1954, two years before his dethronement of Stalin's "cult of personality" at the 20th Congress of the CPSU, the following amounts were given:
"as from 1921 until present day, for counter-revolutionary crimes 3,777,380 people were convicted, including 642,980 given the highest measure of punishment, 2,369,220 imprisoned for 25 years or lower, 765.180 exiled. "- As translated from V.N.Zemskov's "GULAG" article
In an analysis of KGB's 1988 data, between 1918 and 1953 4,308,487 people were convicted, 835,194 of which were executed.
Collectivization hunger victims / Holodomor
Some consider those who died from hunger during the collectivization period also "repressed". Direct amounts of such victims are not known, but the overall demographic losses during the 1926-1940 period suggest that 9 million people died from hunger in these years. In fact, Ukraine considers their part of the 1930s famine an intentional genocide of Ukrainian population, calling it Holodomor. Many countries support this, including the United States.
According to the papers, "Victims of the Soviet Penal System in the Pre-War Years: A First Approach on the Basis of Archival Evidence" there were only 799,455 documentable deaths from 1921 to 1953. It states that "Mainstream published estimates of the total numbers of "victims of repression" in the late 1930s have ranged from Dmitrii Volkogonov's 3.5 million to Ol'ga Shatunovskaia's nearly 20 million [...] the bases for these assessments are unclear in most cases and seem to have come from guesses, rumours, or extrapolations from isolated local observations. As the table shows, the documentable numbers of victims are much smaller."
The death count proposed is inconsistent. According to Europe: A History, by Norman Davies, Stalin killed 50 million people. Let History Judge by Roy Medvedev says that Stalin killed "millions." R.J. Rummel claimed that Stalin killed 43 million. In Health & Social Change in Russia and Eastern Europe by William Cockerham, it is said that Stalin killed 50 million people (citing Norman Davies from earlier). Some fringe and anonymous sources even suggest that Stalin killed 100 or 150 million. Stalinist Terror: New Perspectives by Getty and Manning, there were only about 9.5 million deaths in the 1930s. According to Victims of Soviet Terror: The Story of the Memorial Movement by Nanci Adler, there were 8-9 million deaths during the 1930s. Even by adjusting for the 1930s when the Holodomor took place, there is a major difference between estimates. How do you jump from 3.5 million to 150 million?
Some historians calculate the projected birth rate before Stalin and then the population after, and use the deficit to calculate the death count. This ignores that famines, war, and tumultuous periods generally result in lower birth rates. Someone who would have had 4 kids only has 2 because having 4 kids during a famine is, generally-speaking, a bad idea.
Others count World War II deaths. Yes, Stalin ignored warning after warning of Nazi Invasion, didn't develop the Red Army that much, and handicapped the Red Army by ordering the executions of 3 of the 5 marshals following the Winter War, but he also had previously attempted an anti-fascist military alliance with Britain and France, both of which declined because they favoured a policy of appeasement.
The 20 million Soviets dead could have been reduced or prevented, but Stalin himself was neither directly responsible for the deaths nor did he order them. Some people (for instance, Dennis Prager in his PragerU video 'Is Communism Moral?') cite the Black Book of Communism. He states, "Here are the numbers of people murdered by communist regimes; not soldiers [but] ordinary civilians." Of course, this would be saying that SS officers and the Einsatzgruppen who collaborated with the Nazis were "ordinary civilians."
The Black Book itself is arguably unreliable. It counts Nazi deaths in World War II as "victims" of Communism (as does the Victims of Communism Memorial Foundation), it counts civilian deaths as a result of the American invasion of Vietnam as victims of Communism, two of the main authors distanced themselves from the book, stating that the main author (Stéphane Courtois) was "obsessed" with reaching the 100 million mark, it counts non-births as deaths (as mentioned earlier), the Black Book adds additional tens of millions of deaths for no reason, and it counts anti-Semitic pogromists in Ukraine and the Baltic States as "victims of Communism."
While you have to admit that Stalin's collectivisation policies were a major contributor to the famine, and the Central Committee had available grain reserves and was exporting grain at the time which certainly didn't help, I believe that the situation was a bit more nuanced than deliberate genocide. In 1932, there was a major drought that affected the produce. The USSR had previously been ravaged by World War I and it is possible that the Soviet leadership simply didn't know about what was happening. According to secondary sources, the actual harvest was only 40% of what was reported, which would suggest that mid-level party corruption was to blame. Many kulaks also hoarded grain and slaughtered their own livestock to fight the collectivisation movement.
There was a lot of suffering. 3.5 million deaths isn't somehow better than 20 million. But for the sake of historical accuracy, it could be reasoned that a better generous estimate would be 7 million deaths.
While these three categories are far from the only ones considered by modern historians, they are the most widely used ones most agree on. Even they still show the Stalinist repressions' scale to be wider than many others.
The overall number of people repressed in the Stalin era mostly depends on what one considers a "repression". The strictest definition (those convicted for counter-revolutionary crimes) would include about 4 million people, while the widest ones (which may also include those given high prison sentences for non-political crimes or 18 million people sentenced for violating "labor decrees") will display up to 40 million.
A communist or a fascist?
Although he was a member of the Communist Party of the Soviet Union, Stalin had a few things in common with modern-day Republicans. One major difference is he was more violent than they are and it's mainly the GOP non-elected officials who are the worst of bad apples. That includes the tendency to invade other countries and an urge to imprison people who disagree with them.
- The Death of StalinThe about.com website isn't peer reviewed but is more often right than wrong.
- The mystery of Stalin's death This is from the BBC.
- Aleskey Litvin: Russian Historiography of the Big Terror(in Russian)
- The Newest Local Historiography on scale of political repressions in 1937-1938(in Russian)
- "The Kulak exile" and deportations(in Russian)
- "The demographic plunder"(in Russian)
- Tauger, Mark (1991). "The 1932 Harvest and the Famine of 1933." Slavic Review. 50 (1): 70-89. doi:10.2307/2500600. JSTOR 2500600.