Many nations did a lot, but i must say Finland, even though i am biased. Finland did not only fight against second largest nation on earth with most tanks and huge superiority everywhere, but at end of the war Finland's population was actually surprised to see war end, they wanted to keep fighting as they believed we could have kept fighting and our army was still undefeated. Censorship has a lot to do with it, but still, when peace came, flags were raised to half mast to mourn the loss of land. After keeping independence while fighting alone against Soviet Union, Finland was mourning loss of land. And Finns wanted it back, and wanted to attack Soviet Union, take back the land and create Greater Finland.
Luckily our leadership at least understood that Finland, with smaller population than pre-war Leningrad, could not forever keep fighting against nation that eventually even defeated Germany.
So we fought 2 wars against Soviet Union and one against Germany and kept our independence, and was never occuppied apart from Hanko. Not too bad. Oh, and Soviets suffered huge casualties.