Let's say you go back to 1927 and shoot Hitler.
That means that the Communist Party wins in 1928. Which means the Molotov-Ribentroff pact still happens, Poland is still partitioned and conquered, Britain is still drawn into war with them, the confiscation of the "rootless cosmopolitans'" wealth still happens and they end up in gulags rather than concentration camps.
The only way that anything actually changes is that there's no Eastern Front, and the French communists conduct guerrilla warfare against their own troops rather than the Germans.
The war would probably have been even bloodier, but France, Italy, and some Austro-Hungarian countries would be on the allies' side so the outcome would be the same apart from Lend-Lease not strengthening the Soviets to the point where they're able to threaten the world for 50 years. Also, the Japanese would have destroyed China completely.
I'm actually not sure whether that would have been a good thing or not.