If someone has not asked for mercy, are we obligated to pardon them?
When Jesus was giving the Sermon on the Mount, he made it clear that we must forgive unconditionally. He says “For if you forgive men their trespasses, your heavenly Father also will forgive you; but if you do not forgive men their trespasses, neither will your Father forgive your trespasses” (Matt. 6:14-15). This is also why unconditional forgiveness that Jesus showed on the cross has become a standard and sign of holiness among martyrs too. Like St Stephen who, like Jesus, prayed for his killers.
This does not necessarily mean that we need to keep up relationships with those we have forgiven. There are cases where associating with some people might endanger us or cause us spiritual harm. We can decide to forgive those people and reduce our association with them or cut ties with them permanently. We forgive everyone, but we must not be close friends with everyone.
If you are ever confused or are in a complicated situation you should ask your priest.