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 at least 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.
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)