Redemption for a Nazi?

I'm reading Mission at Nuremberg by Tim Townsend. In the opening chapter he describes Chaplain Gerecke's moments in prayer with Nazi Keitel in the moments before he was hanged for his war crimes against humanity. Townsend describes Keitel's soldier-like demeanor throughout his trial and emprisonment, but how he broke into uncontrollable sobs while Gerecke prayed with him in his cell. At the hour of his death his mask of pride crumbled. I would assume the illusion fell before the realization that he would imminently face spiritual judgment for his sins.
 

In the debate over the morality of capital punishment, I know traditionally the Conservatives are for the death penalty, while Liberals are against it. I am unsure where I fall on the spectrum, but I know I am glad I don't have to make the decision for someone to die; that in itself might weigh on my conscience as indirect murder.
 

But in thinking of this description of Keitel's last moments, and knowing that most religious folk believe in some sort of post-death divine retribution for sins, or at the very least purging before eternal rest, I wondered if some comfort might be found in the idea of paying the ultimate (earthly) price for one's sins. It might cut one's stint in Purgatory shorter than it would be otherwise, for example.
 

In the DeNiro movie The Mission, the Jesuit missionary who used to persecute the natives climbs a mountain carrying a heavy load of armor(? it's been a while since I watched the movie, and I can't remember the details) in penance and to prove he has since changed. The spiritual leader of the group allows him to do so and refuses to help when he struggles, not because the leader is horrid and judging, as we find out at the top of the mountain, but, as he says to the penitent man (again, I'm not sure if my words are exact, but they are close and convey the gist), "You did not do this so God would forgive you, but so you could forgive yourself." The man had to do something in order for himself to let go of the guilt he held against himself.
 

I wonder if the death penalty would serve the same purpose to a repentant person who had committed a truly heinous crime(s) (i.e. those convicted at Nuremberg). If there is no one who cannot be redeemed by God, then these, too, could conceivably have felt remorse for the part they played in the Holocaust. But how, in the face of such immense evil, could one ever forgive oneself for such crimes?! I wonder if the knowledge that they would soon give their own lives in payment would do anything at all to alleviate the heavy, mortally unbearable, load of guilt that must weigh on them (actually, I think it must surely have weighed on them whether they admitted to remorse or not).
 

Thoughts??