Avenger of Blood?

Joshua 20:1-3 Then the LORD said to Joshua: "Tell the Israelites to designate the cities of refuge, as I instructed you through Moses, so that anyone who kills a person accidentally and unintentionally may flee there and find protection from the avenger of blood.

At first glance, cities if refuge seemed a bit unfair. Had I lost a wife or child, I would want immediate justice. It seems that the person guilty of the death, would escape judgment.
But justice and judgment are two separate things. Basically the offending party imposes justice on himself in the form of ‘house arrest’ until the death of the high priest of the city of refuge. At which point he is returned to the city of the victim to stand trial. So basically, it is delayed judgment.
So many times we see wrongs go unpunished….because there is no fair form of imposing justice. But there will be judgment.
Cities of Refuge were positioned within a half days journey from anywhere. They were always accessible. The roads to them were in excellent condition and they were well marked. Once inside the ‘avenger of blood’ could not harm the accused.

I know I am glad Jesus has become our ‘City of Refuge’. Question is, who is the avenger of blood? My stab at it….is God. God is the one that requires shedding of blood for the forgiveness of sin. What say you?
Psalm 142 4 Look to my right and see; no one is concerned for me. I have no refuge; no one cares for my life.
5 I cry to you, O LORD; I say, "You are my refuge, my portion in the land of the living."
6 Listen to my cry, for I am in desperate need; 
 rescue me from those who pursue me, for they are too strong for me.