Youre slamming in open doors. Anyone who know one or two things about WW2, is aware of the Allied effort in North Africa, Mediterranen and Middle East. I already mention that the victory over Nazis was a combined Allied effort. Still its clear that Soviet faced the hardest battles and remained most devasstated after the War, having lost nearly 20 million people.
France, Benelux and Scandinavia gave up without any significant fight. Spain kinda remained vague and was spared, Italy was an ally so again spared. Baltics and Finns were Nazi allies.
It was Britain and Soviet who stood alone against the odds for long periods. Britain was never invaded but Soviet wasnt nearly as lucky.
The Soviet victory over Nazi was in many ways one of those rare comebacks, because they were on the brink of collapse. When it got its things in order, it began griding victories, albeit with huge losses, but eventually steamrolling into Germany by the end of the war.
One big factor of why Russian lost so many people was that Nazis really hated slavic people. When they occupied Scandinavia forexample, they threated the civilians relatively well compared to what Slavic Russian had to go through. Much of the railways in Northern Norway forexample was built by Nazis with Russian prisoners of war. Many of whom died from inhumane laboring and horrible conditions in concentration camps.