Christians, prove your minds aren't molested by fear.

[Mudhammam]

I can't answer for you. I can only answer with what I believe to be true. Justice means the same thing to you as it does to me.

Clearly, this is not the case. In my mind justice is an elusive suitcase term that only begins to really mean something when enacted in practice, and doing so involves taking into consideration as many facts about a situation as possible. It also means that value and appreciation of human nature is assumed. If I don't value the conscious experience of sentient beings, how can I ensure that justice is carried forth? I don't see how I can. So as I'm a humanist and you're a Christian, I'm sure our conception of justice is going to differ from the start (you think human nature is inherently or essentially corrupt, that all deserve death for their imperfections, whereas I think those types of labels are nothing more than our own mental constructs created to guide us towards whatever it is we conceive as progress or improvement).

If a person is living in a way that harms their own life (dogma: apart from God), then that's the level of death he imposed upon himself.

Define "apart from God" and why this is necessarily harmful. For example, as a Christian, I believed I was close to God because I felt all the emotional highs Christians describe when having a religious experience. I see now that those peaks had nothing to do with the doctrines of Christianity but rather only with the conscious state of mind I brought upon myself through fellowship with other like-minded individuals, training my mind to believe certain things about objective reality and my conscious relationship with it, singing worship songs intentionally written to pluck at the heart strings, etc. I can do those things without Christian faith. I can study nature and receive the same feeling of internal warmth and sense of connection with a higher power, the natural Universe. Why or how is this manifestly harmful? To me it appears at least more intellectually honest as I'm now open to receiving new information and can genuinely consider opposing perspectives (granted they're supplemented with scientific experiment), so on that level I see it as less harmful than my former faith in Jesus. How have I imposed death on myself through this alternative view of myself and the world in which I exist (or it through me)?

If someone who has committed a serious act damaging their own life, but now lives not harming it,

You mean they've believed that the essential point of the Gospel is true? Or you mean they've done something more? And without sufficient evidence...which leads me to ask, how is faith virtuous?

and has truly made up for the bad things they've done...

Have they? In what way?

in true justice... which one is deserving of further punishment? This is perfect justice as you would see it. It wouldn't be different to what you think is fair.

It depends. On the extreme level, take Hitler and Gandhi. One claimed to be Christian, the other did not. If it turns out that Christianity is true, on your belief system, there could be perfect justice in Hitler residing in heaven because he had a genuine conversion during his final moments on Earth while Gandhi is in hell for retaining his Hinduism or whatever he believed that rejected Jesus as savior. I'm not arguing that this is the case. What I'm saying is that in perfect justice, this could never be the case, and on Christianity, we're told the contrary is true. This is even demonstrated in the tale of the two thieves on either side of Jesus during the crucifixion, in which the point is clearly made that sinners can be redeemed at any time, even moments before death. So a person's works has nothing to do with their salvation (and Paul seems to emphasis as much) and yet we're to think that justice which relates to a person's beliefs and not their actions is superior in some way?