When the Nazis lost, the Germans didn't get to decide for themselves what punishment they should face. Well, in the East, anyway. It was right when the victims then pursued vengeance against their oppressors and it was also right if they didn't. How this vengeance manifests in a courtroom setting is heavily dependent on context, and until we have war crimes tribunals for the US, it's useless to speculate on how that might happen.

And you can't have it both ways. You can't just ignore what the victims want when what they want is severe punishment and then be all about listening to their wishes when they express forgiveness. If they do, ok then, but what about everyone else they harmed? If you're dealing with a paper-pusher you can't possibly track down every single person who might have been affected by their actions and tally the score. In the rare instance that there is like one victim and they forgive the soldier, then fine. But I don't think it's possible to have such heavily localized effects. If you serve in the military the likelihood that you've only ever impacted those you've directly met is near-zero.

Imperialism is just wrong. Re-education should be the very, very least of postwar justice.

And anyway, I believe that when you kill somebody the only person with the right to forgive you is the person you just killed.