The fact is that the Nazi "Final Solution" was a state sanctioned genocide done in compliance with the law of the land at the time. That the German population as a whole was ignorant and not directly complicit in the execution of the policy, is a small saving grace. However, I asked my German inlaws if they were aware of the program. Answer - "It was in your best interest NOT to be aware." Train loads of people going to a few select locations and no one ever leaving, the smoke and smell of the crematoria; all clues that something was amiss.
The treatment of the German military post-war was retaliatory in nature for the excesses of the Wehrmacht and SS in occupied Europe.
As for the excesses of the Japanese Imperial Army, they have to be viewed from the brutality of the Samurai Bushido code whereby an enemy is a lesser being, particularly if the enemy surrendered rather than fight to the death. That paralleled the Nazi "Ubermenschen" mentality that regarded anyone else as "Untermenschen".