There is no justice in the world.
You cannot practice justice, or eye for eye, in this world.
Why cant you practice it?
Every person has done bad things in life, but there is no effective way to punish every person proportionally to what they have done.
This is especially so because people dont have equal life quality to begin with. Some people have horrible lives while some have easy lives. So you cannot apply same justice or punishment to those two, because if you did, then one would still be punished more than the other in total.
There is basically no way to calculate what amount of justice to apply, since every person lives a different life.