IMHO, the worst crime of WWII and the postwar era is that we failed to make Japan admit and atone for their wartime atrocities. The emperor should have been publicly executed and Japan's school textbooks should have been made to cover their wartime history. MacArthur was basically the absolute ruler of postwar Japan and did not want to shame them, which they sorely needed.
As it is, Japan to this day views itself as the victim, not the aggressor, in WWII. There is zero mention in their textbooks of their atrocities in their occupied territories. They did stuff in China the Nazis could never have thought up. Read up on their experiments on Chinese civilians in Harbin -
Unit 731 - Wikipedia, the free encyclopedia
And when Iris Chang wrote The Rape of Nanking, it wasn't translated into Japanese for 10 years because they couldn't find any Japanese historians who would agree to review the translations. They have never apologized for their crimes or even acknowledged them. They've pretty much had the exact opposite treatment as the Germans did and with the exact opposite results.