Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written, “Vengeance is mine, I will repay, says the Lord.” - Romans 12:19
In such cases, we must leave it to the law to faithfully carry out justice (Romans 13:4), and ultimately to God who will bring them to account on the last day (Acts 17:31). However, the Christian should pray for them that God may change them and save them.