That's a matter of opinion, largely.

I see justice as a tool to enforce the good order and progress of society, with sanctions being administered to discourage unjust behaviour, and punishment having the aim of demonstrating how one's actions have harmed others, rather than simply allowing the injured party to hurt the other in turn. As such, for someone like a Forsaken, who stands in knowing and deliberate opposition to ordered society, justice is really irrelevant, because the individual will not become a functioning member of society. These people ought to simply be removed, punishment is without value, that would just be inflicting harm on someone without purpose. When Demandred dies (for good), he'll cease to be a threat to people and the world, and that's all there is to it.

Essentially, this is why I believe that an ideal justice system would be initially light on sanctions, focused more on the rehabilitation of criminals, and then mercilessly harsh on recidivists, because once you've demonstrated you are unwilling or unable to amend yourself, you're really just a drain on our time and resources.

'Course not everybody shares such an opinion, which is presumably why the concept of judgment and torture in an afterlife is so popular.