I honestly don’t think people can change. At least not drastically. I think you can try and be a better person, but that part of you that you tried to distort and make acceptable to others, it’s still there … festering.
You can change the phenotype, the outward characteristics, the way you are seen by others. But you can’t inherently change, you can’t alter the gene.
Unless, of course, you get radiation poisoning, y’know