Does "mercy" mean that we should let criminals get away with crimes?

How does Jesus's view of pacifism ("do not resist an evil person", "turn the other cheek", "I want mercy, not sacrifices", and "do not repay evil with evil") line up with the country's court systems and justice in general? 1. Why if someone kills my child and then I kill him, it is a sinful "revenge", but if brought to court and imprisoned it is not a sin? Isn't sentencing someone to lifetime prison for example "repaying with evil", too? What if the prisoner really repents and changes his life, but they never let him out and let him die there? 2. Why if I kill someone evil to stop him because he is a serial killer? Am I sinning because I am "resisting"? 3. What should I do if someone attacks me or my family and threatens their lives? Should I turn the other cheek? 4. Why is it a sin to stop (kill) someone who is well known evil person (e.g. drug dealer, killer, or rapist), but he is paying the court system and he never gets caught and sentenced? Why are we supposed to tolerate that? Because "it is not our job"? Did God appoint "jobs" only to certain people to seek justice and protect their neighbors? We are the image of God, we are supposed to dominate the planet and keep everything in place. In many occasions, evil can be stopped only with the death of the evil persons doing it. How is that supposed to work if we are also supposed to be like "sheep sent amongst wolves"?