Aleading soviet writer of the 1950s and winner of the nobel prize was

The correct answer is Boris Pasternak

He was a really important writer throughout the world but was disliked by the USSR regime because he criticized them in his works. When he won the nobel literature prize they forced him to decline it and it was only in 1988 that his family managed to accept it in his name since he declined out of political pressures. This makes him the only author that received it posthumously.