Any Soviet official after 1938, so no Trotsky or longer living Lenin. Who would you want to win the power struggles? Best in this case mean strength of the USSR, so no leader who immediately breaks it up Particularly looking for who could best compete with the USA, instead of being overshadowed more and more. Only during Stalin's reign did the distance between the USA and the USSR decrease but the USSR never surpassed the USA I'm of the opinion that almost anyone could have led the soviet union, from generals to minor officials. Infighting between other competitors can lead to even a black sheep winning never mind an underdog. So assume a lucky pod, who's your bet?