Is the universe just?

[anagogy]

anagogy, can I not theoretically go out and kill a bunch of people in sheer negatively-polarizing bliss, die, forgive and accept myself completely, continue reincarnating and have no guilt and nothing to repay to these people at all?

Doubtful.

The degree of forgiveness would needs be directly proportionate to the amount of pain you were directly responsible for.

Note that in the example you quoted above, that Jesus was only absolved karmically of the death of another, when he forgave the people who were doing the same thing to him? Forgiveness stops the wheel of karma, but it has be proportionate to the imbalance.

In other words, its harder to forgive yourself for heinous acts than non heinous acts. Especially in a pure soul state.

For one thing, to forgive yourself you would have to fully understand the ramifications of your actions. That in itself is a study.