The parable Jesus told in the book of Matthew 18:31-33 talks about forgiving one another, and this applies even when the person who did the wrong against you does not repent or acknowledge his or her wrongdoing. We must forgive no matter what. It is easier to forgive when the person who did wrong apologies or asks for forgiveness. But it is much more difficult to forgive when the one who wronged us does not acknowledge the hurt or is not even sorry. But that does not matter, we still must forgive, just as our Father in heaven forgave us and paid our debts of sin, we must forgive others.
Beloved, do not avenge yourselves, but rather give place to wrath; for it is written, “Vengeance is Mine, I will repay,” says the Lord. Rom 12:19 And also: There is one Lawgiver, who is able to save and to destroy. Who are you to judge another? Do not grumble against one another, breathren, lest you be condemned. Behold the judge is standing at the door! James 4:12 and 5:9 When we try to seek revenge or avenge a wrong, then we make ourselves out to be a judge. Only God can be Judge. But, Jesus did not wait for us to come to him and say we were sorry. While we were still sinners, he died for our sin. So, therefore why hold out a grudge waiting for an apology or for a wrong to be made right? We must not do that. We must forgive regardless of whether we receive an apology, or whether the wrong has been corrected or not. In Hebrews 12-14-15, the root of bitterness can cause a believer to become defiled! This is a warning for us not to harbor feelings of anger, offense, resentment or bitterness. Even when we think it is well deserved. Ephesian 4:31-32 Let all bitterness, wrath, anger, clamor and evil speaking be put away from you, with all malice. And be kind to one another, tenderhearted, forgiving one another, even as God in Christ forgave you.
In the Old Testament, otherwise known as the Old Covenent, in Leviticus and Exodus, there are many examples where God tolerated the right to seek revenge or collect on a debt. Under the old covenant, the Law was the authority. But now we are living under the New Covenant, and new covenant believers are addressed differently. For example, look at Matt5:38-42 how Jesus renounces the old testament laws.
Sometimes even when you do good to another you will be rewarded with evil as in Psalm 35:11-12 and 13-14. Nevertheless as Matthew 45:44 says - But I say to you love your enemies, bless those who curse you, do good to those who hate you and pray for those who spitefully use you and persecute you.