When I first was reading Russian history, it was thought to be Malenkov, because he was chairman of the Council of Ministers and secretary of the Party. But it seems as though now there's an acknowledgement that Stalin's team and pallbearers ( Malenkov, Beria, Molotov, Khrushchev, Bulganin, Mikoyan, Kaganovich, Voroshilov) initally formed a collective leadership that was able to cooperatively do some things they had long recognized to be needed, but unable to be done while Stalin was alive, like release the victims of the Doctor's Plot ( which is thought likely to have been the beginning of a new Purge by Stalin, interrupted by his death) and stop the trend towards official antisemitism, reduce the Gulags, try to get along better with the West, more attention put to producing consumer goods.... Fairly soon, however, Malenkov, Beria, Molotov and Krushchev began to meet together more often, preparing a common agenda for meetings. Then Beria became more and more assertive, confrontational, of the rest of the team, infringing on their fields of authority. As head of the secret police, Beria was also in a very strong position to take sole control, and, becoming apprehensive, the entire team ( under the leadership of Khrushchev) ousted him in June 1953, executed him in December. After Khruschev's "Secret Speech" in 1956 denouncing Stalin's Great Purges the team became more shaken- Khrushchev came off looking best, Beria the worst, but some of the team, like Kaganovich, had obviously bloody hands. Khrushchev was able to edge forward, and eventually by mid 1957 he and his people were in power.

Fitzpatrick: On Stalin's Team