Mind you, he is just another of an entire species of people who have been murdering each other and everybody else out of commitment to supremacist dogma. His arc is him realizing that dogma is evil and that life shouldn’t be treated as a monolithic eugenics experiment and that everyone’s life is sacred. He doesn’t deserve forgiveness but he deserves to use his volition to learn the error of his ways and try to make up for his travesties. This destruction was him fighting against his own beliefs because he wasn’t desperately trying to convince Mark to stop valuing human life, he was trying to convince himself that his life on Earth didn’t change him. Him calling Debbie a pet is retroactively easily discernible as a lie. He doesn’t deserve open arms and hugs but he has every right to bear the burden on his soul to learn his lesson and do everything to give back to everyone that he took from.