From the start the Germans were loosing officers, time, and transport vehicles at an alarming rate. Battle of Moscow was a major defeat but if your asking about when did shit hit the fan it would be Operation Uranus. The soviets counter attacked & encircle German troops at Stalingrad and wiped out the 6th army (the elite German army btw), part of the 4th panzer army, and Axis allies (Romania & Hungary). Soviets were able to encircle the axis because they picked on the weaker Romanian troops rather than the Germans. An invading force of ~1 million Axis troops, 91,000 remained and surrendered at Stalingrad. After POW camps, only ~2000 survived by 1955. Not only did they loose men, officers, morale, and equipment, loosing Stalingrad meant that the Germans lost their chance at controlling the cities of Baku and Grozny. Baku and Grozny were crucial bc they produced 80% of the soviets' oil while Germany was desperate for oil.

The Japanese...well they never really had a chance at winning. The Americans had a better navy and air force while the Soviets had a superior army. Plus both were industrial giants and technologically advanced (if the Wehrmacht couldn't take both on what chance did the Japanese have). And no amounts of samurai warriors or Shinto gods could save Japan from the atomic bomb. So for the Japanese as soon as the Allies were done with Germany, their screwed and are delaying the inevitable.

Italy just sucked ass in the war. Mussolini thought he could take Greece but couldn't so he needed Germany to bail him out. This delay to help Italy costed Germany time that could've been used to reach Moscow faster.

So to sum up in the Eastern Front Germany needed better allies and they should've tried to decapitate the USSR, not try to occupy it.