What were the successes and failures of Stalin?

I agree that collectivization and governmentalization of eveything paved the way for long term failure, since such policies deprived many people of an incentive to produce. The purges, however, were not necessarily a "failure." Even though Stalin obviously overdid it, the purges at least accomplished the vital task of crushing all hint of opposition prior to WWII. That was very important since the last thing the USSR needed were internal power struggles while the nazis were plannning to wipe them all out. Stalin rapidly industrialized the USSR, and, with the huge forces he built, repelled nazi invasion--an achevement which stands in stark contrast to the failure of the western democracies, which were routed in a matter of weeks in 1940. Among the bigest victories were the battles of Moscow late in '41, Stalingrad by early '43 Kursk in July '43, the smashing of the reich's Army group center in the summer of '44 and the capture of Berlin the following year. Stalin went on to meet the challenge of the USA after the war, matching the US in nuclear weapons, dominating eastern Europe and bequething superpower status to his successors.