<h2>Answer:
<u>Russia reaching berlin, and the US dropping the A- Bomb on Japan.</u></h2><h2>
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If you mean what LEAD TO the end of the war, I would say that would be the fact that Germany lacked the resources to keep going, because, after 1941, they were fighting the US, the UK, Italy, Russia and a few other countries mostly by themselves.
A big turning point in the war was the German defeat against the Russians in the battles of Kursk and Stalingrad. The Nazis were in gradual retreat after that.
One thing about Japan, yes the atomic bombs ended the war, but Russia also invaded at the same time. You might not think that would matter, but I've read about it, and apparently the Japanese had fought a bit against the Soviets in 1939 before WWII started and the Japanese lost very badly, so the Soviets were a factor in the Japanese surrender too.
I am a history major, so this is all from memory, but it should be easy to check by searching some of the key names.