Lenin's initial plan was to make Russia communist by going through socialism first, as Marx laid out in his Manifesto, and then spreading the ideology to Europe. Stalin then came in and "Socialism in One Country" was his policy until after World War 2, when he took over Eastern Europe and made them puppet states as a guard from the West.
So Stalin was a socialist dictator, but he can't be a communist dictator because 1) The USSR was never technically communist, and 2) Communism can't have a dictator