Hitler made mistakes.
Hitler single mistakes that cost him the war was declaring war on the United States, and allowing the German army and Gestapo/SS to treat the Polish and Russians badly (they probably would have joined with him against Stalin). Japans single mistake that cost them the war was attacking Pearl Harbor and not the Russians.
Everything after that involved the United States and US war production which was so disparate, that he War could only end one way.
I don’t think the Japanese would have done very well against the Soviets. They fought two campaigns against them (”incidents”) and were very roughly handled by the Soviets. If nothing else, the Soviets had MUCH better armor and artillery than the Japanese.
Also, IIRC, when Hitler declared war against the US, he was looking for Japanese to declare war again the Soviets - which didn’t happen!!