There are some Christians who believe that forgiveness goes hand-in-hand with repentance. And certainly, the unrepentant sinner will not inherit the kingdom of God. However, there is a difference in forgiveness between humans and eternal forgiveness between man and God.
In what we can forgive, yes, but I don't see the difference concerning when we should forgive.
Where does Christ tell us to forgive those who have done wrong, continue to do wrong, and are totally unrepentant in doing wrong.
Followed to its logical end, this would mean that having a prison system is unethical.