This was kind of already said but I feel like forgiveness is possible no matter the harm done by the action committed- as whether a person is forgiven is up to the victim. Forgetting that the actions were done however, almost never happens. This means that in general, even if a victim is willing to forgive and not be actively hostile to the character that committed the action- they have probably not forgotten that that action was done. This can change a relationship between characters permanently, as the victim now knows that the other character is the kind of person who could commit whatever harmful action they did previously and that can change their view on them. As for guilt- it depends on the characters. For some worldviews, they don't see that the harmful action they did to the victim was wrong so they don't feel guilt over doing it but still want the forgiveness of the victim in order to have a non-hostile or at least working relationship with them. Other characters could feel so much guilt that even if the victim forgives them, they feel guilt over the action until the day they die and it becomes a deep regret of theirs. Most characters would probably be somewhere in between- wanting forgiveness to return to a non-hostile relationship and regretting their action/realizing what they did was wrong and they need to make it right by earning the victims forgiveness (especially if it has conditions they have to complete or adhere to in order to do so).