I feel like we could be way more creative in how we treat prisoners in how they “repay their debt”. Someone like Ongwen could probably be very valuable in finding and converting other people away from situations similar to his. Or from helping security forces secure against the kind of tactics they used...

I don’t know random thoughts, but we can punish someone and have value generated at the same time.

Deterrence, incapacitation, rehabilitation, and restoration are pretty self-explanatory, and the reasons for those are clear. Denunciation means crimes are punished in order to send a message that such behaviour is condemned. But is there a good reason for retribution?

The meaning of retribution is that those who have hurt others suffer real consequences. This isn't necessarily something sadistic, as there are a number of reasons why this can be a valid purpose. You want people to have faith in the justice system, to not believe that people are getting off with slaps on the wrist, that mass murderers aren't being pampered, and so on, so that they don't turn to vigilante justice. It could be the case that, e.g., Brock Turner was unlikely to ever sexually assault a woman ever again after three months' jail time. But the perception that he was let off lightly could undermine faith in the justice system.

In a case like this, it may be that his victims need to see that he is punished so that they can have faith in their justice system. Whether or not that is the right call here, I don't know enough to make a judgement. But I don't think one can entirely ignore retribution as a purpose.

Presumably the child of a war criminal would also have suffered trauma in youth, but there would no consideration of mercy, or sympathetic longform articles for the 30something 2nd generation war criminal. They would be simply be treated as evil.

Well I'm glad that solutron from Hackernews has figured out the one true morality for everybody. Thanks solutron from hacker news!