Are there acts so terrible that you should not, as you say, give a gift to the other?
Some people will not forgive certain people for certain acts. Yet, other people will forgive others for the exact same kind of act. Thus, it seems to me that it is not the act itself that is out of bounds to forgiveness. Instead, the one who was injured is not ready to offer forgiveness. We have to be gentle with people under these circumstances. We are not all ready to forgive others at the same point of the injury. We have to be careful not to condemn those who need more time or who are ambivalent about forgiveness in a particular circumstance.
For additional information, see Why Forgive?