Technically speaking, I don't think we are able to forgive anyone unless the person confesses his wrongdoing, repents and ask for forgiveness. God doesn't forgive us either unless we confess and repent. The offender has to take the first step. That doesn't mean that you don't love the offender.
We are called to love everyone.
1 Corinthians 13:4-7:
4 Love is patient, love is kind. It does not envy, it does not boast, it is not proud. 5 It does not dishonor others, it is not self-seeking, it is not easily angered, it keeps no record of wrongs. 6 Love does not delight in evil but rejoices with the truth. 7 It always protects, always trusts, always hopes, always perseveres.
Love "keeps no record of wrongs" doesn't mean that you must forget the offense, or stop being upset about it/evil, put it under the rug, etc. I believe it means you have to stop bringing up the offense to the offender to as a form of threat, to make him/her feel guilty, etc. like picking at an old scab.
If someone confesses and asks for forgiveness 70 times the Bible instructs us to forgive. However, it is up to God to decide if the offender was genuine. If the offense is of a criminal nature, most people would not confess. I read somewhere most prisoners believe they are innocent (at least partially).
Forgiveness for our own wellbeing/good is modern psychological teaching, but it is not Biblical forgiveness.