The unforgivable thing does not exist. No crime is so serious that I will refuse to forgive you. Even the harshest religion of human beings spread the truth.
These religions may be controversial in the way of redemption. They may be controversial on the way of salvation, but they all agree that such a way and way is there.
When you are the moment of death, you will naturally get the opportunity to redemption.
The so-called redemption is to realize that you and all other people are one. That is to understand that you and all things - including me - are one.
After death, when you are separated from your body, you will have it immediately - remembering - this experience.
All souls experience their "unity" in the most interesting way. They will get the chance to experience every moment they have just completed, not only from their perspective, but also from all the people affected by the moment. They will rethink every thought, rephrase every sentence, do everything again, and experience the impact on every involved person, as if they are the same as others -- and they are indeed others.
They will experience their identity with experience. At this moment, "all of us are one" is no longer a concept, it will become experience.
The place where you have endlessly tortured and cursed does not exist, and that is written by your theological theory. But you - all of you - will experience the effects, consequences, and outcomes of your choices and decisions. But it is about growth, not "justice". This is the process of evolution, not the "punishment" of the god Buddha.
In your "life review" some people call it -- in the process, you will not be affected by any one trial, but have the opportunity to experience the whole you in every moment of life to experience things, rather than those living in the flesh, you have experienced something of the individual.
What you have experienced is not pain, but awareness. You will understand deeply, deeply realized each time overall and its implications. However, this will not make you miserable, and it will bring you into the light.