Twenty million Russian dead in World War II. Many deaths can be attributed to the Soviet method of combat and many more to just plain incompetence, but one cannot ignore the sacrifice. In many ways it was Iran versus Iraq, but played in the 1940s. We could not afford Hitler winning, but the aftermath of Stalin winning wasn’t so great for Eastern Europe either. And of course the Russians today (and the Soviets then) never mention Allied support in the way of convoys to Murmansk and material supplied via those convoys and overland through Iran.
It’s also very unlikely that the allied victory wouldn’t have gone the way it did if the Soviets were not making Hitler bleed on the Eastern Front. It’s easiest to just acknowledge that both the US and the USSR made the victory possible. The Russians freely admit this, only the US tries to be to arrogant as to ignore the importance of the Russians.
Lets not forget that the Soviets initially allied with the Nazis.