1942 Stalingrad

HUGE in the irreplaceable losses and the exposure of Hitler as a tactically and strategically incompetent egomaniac. After Stalingrad it was only a matter of time until Germany fell, not to mention that plots from within the German army to replace or kill Hitler as a means of securing some kind of settlement with the Allies went into overdrive.

I believe this was the deadliest battle ever. Over one million people died

This battle was very important, but I completely agree with PzK perspectives, that the key was Moscow, and not Stalingrad. Anyway, it is indeed was the huge lost of the German Army and a lot of prisoners taken, with their commander, Paulus.

This absolutely was the turning of the tide. The Germans really never were able to gain the ascendancy thereafter.

The end of Germany. A loss of many a fine troop on both sides. The German 6th was probably the finest infratry in the world. Only a few thousands ever returned home.

No doubt that this was important. If the Soviets lost, then Hitler would've expanded his Nazi empire, victimizing more people and employing others to do his evil biddings.

Hugely important, but without the defense of Moscow, there would be no Stalingrad and without a victory at Kursk, Stalingrad's importance would be less. So, maybe the entire Eastern Front should be considered one battle for this list, as Moscow, Stalingrad, Kursk, Leningrad, Konigsberg, Bagration, Berlin and some of the other battles like Kiev (that slowed Guderian's Panzergruppen) were all important. Hell, Italy's half-ass performance in Greece is important. Although very important and the one true turning point of WW2, the war itself did not have some of the important implications as other wars and battles featured on this list. Maybe in 100 or 1000 years, the true importance of WW2 well be known, but for now, there are other wars that were more important, and thus their keys battles are also more important.