I voted for 1941; because that’s the last year during which the Axis had a real chance to win the war. It’s also the year the Axis made the major decisions which would later result in defeat.
In the spring of '41, Germany invaded the Soviet Union. In December of '41, Japan (and later Germany) went to war against the United States. Suppose, for example, that the latter decision had not been made. The United States would still have sent overwhelming quantities of weapons to the Soviet Union and to Britain, and would still have attacked German ships in the Atlantic. But probably, political factors would have forced the U.S. to maintain the fiction of neutrality, at least for a few more years. The U.S. economy would not have been fully militarized during those years. Also, Germany would not have had to worry about the U.S. Army. That army helped with the invasion of Algeria in 1942, of Italy in '43, of France in '44, and of Germany itself in '45.
In 1942, Germany attempted to conquer all of the Caucasus, and succeeded in conquering a significant portion. Had its plans been fully successful, it would have had the oil, grain, rare metals, and a portion of the industrial capacity and labor force required to keep pace with the Anglo-American air war against it. At that point, Hitler might have attempted to negotiate a peace treaty with the Soviets; especially as it was becoming clear that Soviet resistance was stiffening. Future gains at Soviet expense would be far smaller and far more expensive than the gains Germany had achieved up to that point. Stalin might well have agreed to a peace treaty, because his goal all along had been for Germany and the Western democracies to bleed each other white while the Soviet Union did nothing. For the Soviet Union to bleed itself white, while the Western democracies fought no major land war against Germany, was more or less the opposite of what he’d wanted!
With the ultimate resolution of the Nazi-Soviet war postponed by mutual agreement, Germany would have been free to focus a larger portion of its war effort on the British. Possibly, this might have meant turning the Mediterranean into an Axis lake. Or it might have meant a few years of stalemate, followed by the use of jet technology to control the sky above Britain. That control would have been followed by a land invasion of Britain itself; and an end to Germany’s war in the west. At this point, Germany would be strong enough to make Stalin think twice before invading! The result would have been the realization of Hitler’s dream of a Germany too strong for anyone to ever again impose a Versailles Treaty on it.
In the Pacific, Japan might have been able to have gotten away with seizing British and Dutch colonial possessions without the U.S. going to war against it. Other than the lack of the Philippines, Japan would have been able to build more or less the same Pacific Empire it ended up building. Except that it wouldn’t have had to worry about the U.S. Pacific Fleet and Marine Corps taking that empire away. China would still have been a major thorn in Japan’s side, and it’s doubtful it could have taken India, except perhaps in the early, heady days of conquest. Stagnation on the mainland Asian front would perhaps have been followed by peace treaties. Or perhaps Japan would have been pushed out of some of its mainland Asian possessions, while retaining others. But absent a war with the United States, Japan would probably have emerged from WWII with its Pacific empire more or less intact. This is especially true if Germany had conquered Britain.