Natal issues might give tendencies, but challenges in the current sphere can take that away requiring an extensive look at the 2ndary, tertiary, and minor progressed return charts (using the Quotidian Bija MC midheaven progression). While one might have a natal tendency to forgive, it does depend on how significant the transgression is in the current life challenges. And then there is the situation where through whatever mental development the person learns to accept the difficult behavior not as needing forgiveness(who the hell do they think they are that they have to forgive) but with gratitude for the bad thing that was done cause that person karma just that you could in the future not have to do it yourself and enable more karma to work off.
Astrologically it depends on how the person can deal with change which entails many many different interactions of the Moon, as well as how their brain works which is dealt with by Mercury, Saturn, and Jupiter. I should think that if their natural tendency as shown by their asc to fight or flight so that the fight tendency is less likely to be willing to forgive than the flight tendency which at least gives more time for thinking before actions. And then one needs to know what the state of their own wounds are by looking at the asteroids Nemesis and Psyche as they aspect Mercury, Saturn, and Jupiter. And then there are a whole series of other asteroids which if aspecting the three major planets of cognition can impact the ability of the individual to be flexible enough in thinking to make this major jump(18 of. them actually).
And to follow that up one really needs to look to see if they have the astrological markers of Narcissist Personality disorder, since the whole concept of forgiveness is beyond the ken of them.
Age also has a lot to do with it. The older a human gets the more rigid they become in their ability to change their minds about anything, so the chances of forgiving after the 2nd Saturn return are seriously diminished.
I could go on, as I’ve only scratched the surface of what I would need to look at to answer your question.
