I mean if the villain’s redemption is well written then typically the guilt from their past actions is the punishment for said actions, and their current actions are largely focused on atonement and reparation. That sort of thing often makes them even more relatable because while not everyone has killed another person, everyone in the world has hurt someone else at some point, maybe unintentionally, maybe unknowingly, maybe due to extenuating circumstances or their own trauma, or maybe because they were just a worse person at the time. Does that mean they are never allowed to be a better person and must eternally suffer for all the wrongs they’ve committed? Is it not better to encourage their goodness in the present than to forcibly drag them back to when they were bad over and over again for the sake of vindication? Does society really benefit from that sort of thing? And what if they end up saving more lives than they’ve taken? Something to think about.
A good percentage of my novel (WIP, third draft) is about that. It takes place in this space age afterlife where objective and good space angels categorize and separate people by the development of their consciences. And the villains’ activist group is in the self-righteous category, and they don’t believe in the forgiveness and redemption of many kinds of people. The two main antagonists are a husband-and-wife duo, and the husband is bitter from tragedy after being one of the earliest fighters for womens’ votes in the US on Earth. He ends up coming to terms with the harm he’s now caused in the afterlife in the name of revenge against wrongdoers; and then the protagonists convince him that he too has the right to atone by being— and by doing— better.
Admittedly, since in this universe people can be reincarnated indefinitely, the harm that people cause (whether back on Earth or in this afterlife) is softened. As an interesting bonus, though, I will say that the villains did seize the means of reincarnation and start deciding who gets to be reincarnated— until the protagonists win, of course.
Also also, that theme is just like a quarter of what the novel has to offer theme-wise. It’s also largely about healing from childhood trauma, mental health tools, identity discovery, found family, and kinder perspectives. Also the space angels are super cool and have interesting science-fantasy powers; and the science and sci-fi stuff is really cool as well! (Yes, I did just devolve into advertising. You would have too!)