"Comrade" Joseph Stalin (born as Ioseb Besarionis dze Jughashvili on December 18th 1878, greg.) has been the General Secretary of the Central Committee of the Communist Party of the Soviet Union (Bolshevists) since 1922. Well, that's his title - in practice, he's more like the pope of the Communist church, tsar of Russia, and CEO of Soviet inc.
Although Lenin had made him a member of the Central Committee in 1912, Lenin had also warned the other Communists in his testament of "comrade card index", but even this couldn't prevent Stalin's takeover of the party. Opponents up to and including Leon Trotsky, the founder of the Red Army, were removed from power, exiled or killed. At the end, "comrade" Stalin had absolute power.
He used it to expropriate millions of farmers and collectivize them (which caused a famine killing millions), send millions of people to the Gulags, and repeatedly "purged" the Communist Party as well. In the Tukhachevsky affair of 1937, even the officers corps of the Red Army was purged, which was the reason for it barely being able to defeat little Finland in the Winter War 1939/40.
Strangely, despite being very paranoid, he didn't have any qualms of making a non-aggression pact with Nazi Germany in 1939.
He also has peculiar habits: He dislikes travel, and refuses to travel by plane. He gives nicknames to his favorites, for instance referring to the "poisonous dwarf" Yezhov as "my blackberry".