The USSR under Stalin, conspired with National Socialist Germany under Hitler to precipitate WWII....both invaded Poland in 1939....meeting at Brest Litovsk ,having divided Poland between themselves, for a celebratory victory march past....Hitler proceeded with invading countries to his West whilst Stalin proceeded with invading the Baltic states and Bessarabia.

The USSR fed the German war machine with raw materials, armanents , fuel and munitions as it conquered the countries to its west resisted only by the UK.

That Hitler turned on his ally Stalin in '41 does not give Stalin any brownie points....the USA and the U.K. do get brownie points for pouring munitions and military material and food that helped to rescue Stalin's forces  which helped to defeat Hitler.

Stalin was as much responsible for the millions of USSR deaths and all told WWII deaths as was his partner Hitler.