Perhaps fittingly, history's most prolific executioner, Vasili Blokhin, survived all of Stalin's purges and was finally forced into retirement after Stalin's death.

At the risk of betraying academic impartiality, this man's accomplishments are truly impressive and horrifying. He is credited with personally killing tens of thousands of people, and holds the record for the greatest amount of executions performed in a month's period (7,000 in 28 days, by his own hand).

Vyacheslav Molotov, co-signer of the Molotov-Ribbentrop pact, was affiliated with the Bolsheviks since 1906. Molotov gained influence in the Bolshevik party, joining the Central Committee in 1921, and the Politburo in 1924. Molotov backed Stalin's policies in the mid-late 1920's, and became prime minister in 1930. Molotov became a key figure in Soviet foreign affairs, including the Molotov-Ribbentrop pact, and the Winter War, where the Finns named the Molotov Cocktail after him (not in honor). While Molotov's influence declined in the late 1940's (he lost his position as foreign minister in 1949), he returned to prominence after Stalin's death, opposed Kruschev, and eventually lost almost all influence in the Soviet Union.

Despite his loss of Status towards the end of Stalin's life, Molotov remained unapologetic about the Great Purge, and consistently supported Stalin, and it appears that they had a fairly friendly relationship.

Source (It is a secondary source, although it is online, so I hope it will be acceptable)

One of the old Bolsheviks (party member from before 1917), Lazar Kaganovich, survived being part of Stalin's inner circle for most of Stalin's regime. He infact lived until July 1991, just 5 month before the collapse of the Soviet Union which he helped found.

If you want to read more about Stalin's inner circle (quite a few survivors) I strongly recommend The Court of the Red Tsar by Dmitri Volkogonov.