You can never recompense the damage. Best thing to do is imprison them, and all other life violators in cramped, sparse prison cells. And make them spend their days doing nothing but gruelling work that somehow benefits society. And when I mean sparse, I mean make them sleep on the cold hard floor, feed them only enough to sustain them and do all their business in a drain. Really make them live like dogs.
They'll never know happiness again, and that's the closest thing you'll ever get to compensating retribution. Castration is fleeting punishment; once the pain has finished they'll just find other ways to be happy, and they shouldn't be happy ever again.