There are some circumstances when an injury we have caused has been so serious or so severe that the party we offended may seek some kind of emotional or physical retaliation.  Common sense and prudence, then, must guide our interaction with him.  Perhaps in these situations, it is best to ask for pardon spiritually and then have a Mass celebrated for him.  We do not want our desire for pardon to be a source of temptation for the other party.  We might well be acting more charitably by keeping our distance than by seeking his forgiveness in a traditional way.