I see forgiveness as the unwillingness to become like your violator. Hate makes us reflect back the same characteristics. There is no deeper violation than to become one's violator. There is a type of forgiveness for the worst offenses that does not embrace with naivete', but let's go of hate and the power the violator held over you. This does not require replacing the hate with trust. Forgiveness can be offered as a gift, but trust must be earned. For me, forgiving the worst offenses is letting go of a desire to return the hurt and the sense of desiring their punishment, but at the same time to hold onto a reasoned self-protection based in distrust of the violator, especially if they do not even desire forgiveness. This also protects the violator from more deeply instilling their own cruelty. I won't allow them to destroy myself or their own heart further. It's one thing to forgive a friend who hurts your feelings, quite another to reconcile a compassionate reaction to someone who murdered your loved one.
There is a wise saying, "we cannot hate what we understand". In facing the worst violators it became apparent to me that this statement does not imply excusing behaviors, but that when we understand the deepest forms of hate, we know to run and to not let it grow inside ourselves, but to hone a gentle defiance to be unlike our violator. A second aspect of this saying develops an underlying respect for others. We have not lived any other life, and do not know first hand how the genetic and environmental influences of another person's life would have shaped us. Because of this, there is a fundamental doubt in every scenario that self is in fact superior to its violator in any way. There is no way to verify how oneself would be in another person's life, and for that reason, it makes sense to have a baseline respect regardless of that person's behavior. This means being non-judgmental at one's core. This is the only way I can understand compassion. It must apply to some level in every scenario or it isn't compassion. This doesn't interfere with a reasoned way of limiting trust. Just because I am potentially no better than any other person does not mean I would be trustworthy had I lived their life. So any conclusive judgment on another person is withheld, trust is reasoned and tested over time, compassion is offered freely and as a gift.