Are you saying totalitarian regimes cannot be left wing? Communism is far left and fascism is far right both had one ruling party, with no democracy whatsoever and both were utterly violent in the 20th century.
Not sure if it is impossible but given that left wing politics is about equality and egalitarianism a regime like Stalin's did no more than paying lip service to this. It was in fact nothing more than a far right, fascist, authoritarian, dictatorship which only pretended to have the peoples' interests at heart.