Imagine if you came out of a store and saw a huge dent in your car.  Another driver is sheepishly waiting for you as he stands beside the police officer filling out the accident report.  What will be your response? 
-
In such a situation the Christian response should be to act with meekness and understanding.  “And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ's sake hath forgiven you.” (Ephesians 4:32)
-
Imagine however if after the police report is filed, you find out that the other driver’s insurance will not cover the damage.  You get upset and decide that since you have a dent in your car, the other driver should have a dent in his car too, so with the help of a baseball bat, you place a dent in his fender.   If you took such an action, not only would you have broken the law, but you would’ve also shown your lack of forgiveness. 
-
Romans 12 shows how ungodly a ‘get even’ attitude really is.  “Recompense to no man evil for evil. Provide things honest in the sight of all men.  If it be possible, as much as lieth in you, live peaceably with all men.  Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, saith the Lord.” (Romans 12:17-19)
-
Does this mean that our laws should not hold evil doer’s accountable, but that instead we should just let criminals do what they want to and wait for God to punish them?  Of course not.  God actually uses human governments and the power they have to hold evil doers accountable and God even uses these governments as a means to carry out His vengeance.
-
For example, in I Samuel 15, God used King Saul and his army to punish the evil Amalekites.  During the time of the Apostle Paul, God used the Roman government to hold criminals responsible.  We are told in Romans 13 (right after what we just read in Romans 12) that this is an important function of government and that God uses governments specifically as revengers.  “For rulers are not a terror to good works, but to the evil. Wilt thou then not be afraid of the power? do that which is good, and thou shalt have praise of the same:  For he is the minister of God to thee for good. But if thou do that which is evil, be afraid; for he beareth not the sword in vain: for he is the minister of God, a revenger to execute wrath upon him that doeth evil.” (Romans 13:3-4)
-
By saying that vengeance belongs to God, the scripture is not saying that justice should not be served.  It is telling us that the function of bringing vengeance belongs to God and those He has appointed to bring about vengeance.  That leaves no room for us to take actions simply to get even. 
-
Actions of self defense are not taken in order to get even.  They are actions taken to protect life and limb of self or others, but actions taken because of anger over past actions are not actions of self defense.  They are actions of vengeance. 
-
We can trust God to take vengeance.  He may use others to bring justice in our lifetimes or He may wait until the day of judgment to hold the evil doer accountable.  Regardless, God will be just and we can trust Him.  “God is jealous, and the LORD revengeth; the LORD revengeth, and is furious; the LORD will take vengeance on his adversaries, and he reserveth wrath for his enemies.” (Nahum 1:2)
-
Perhaps you are the one who is deserving of God’s vengeance.  If so, trust Jesus Christ for the forgiveness of your sins so God’s wrath will turn from you.