The biggest damage Hitler and the Nazis did was stop a genuine Communist revolution within Germany. Had Germany genuinely gone Socialist, it’s very likely other highly developed Capitalist countries would have had revolutions as well, and not just the underdeveloped countries like Cuba, China, Russia, Korea, Vietnam, Laos, etc. Had Western Europe gone largely Communist, only the US would really stand as a bulwark of Capitalism, separated by the Ocean, at which point it would have been only a matter of time.

I can’t understate how different history would look today had the Communists succeded in Germany.