Stalin had totalitarian tendencies, ruling by terror. The greater sign were his policies, which centered on government control over every economical aspect, specially the farms, forcing collectivization that led to a widespread famine, killing millions.
Stalin also eliminated anyone who opposed him and even encouraged citizens to spy on one another, killing and sending millions to the Gulag system of forced labor camps.
Additionally, Stalin sought self-flattering and elevation by renaming cities, rewriting history books and ordering songs, books, poems, art, all in his honor. These situations are typical examples of totalitarianism.