Imagine someone close to you got badly hurt. Really hurt. And you're asked: did you want the person to pay for it, or did you want peace? Most of us answer fast. We want them to pay.
There's nothing wrong with that. It's an honest, almost instinctive reaction. The problem isn't feeling this. It's what we do next: pretending the answer is always simple, that "justice" is a clear word with no grey areas.
Every system we accept without question assumes some form of force as a response to injustice. There are courts. There are prisons. There are countries with entire armies dedicated to enforcing limits on those who cross them. No one questions that. The question only shows up when it's a faith, specifically, talking about limits on responding to violence.
The Qur'an addresses this directly, in Surah 2:190: "وَقَاتِلُوا فِي سَبِيلِ اللَّهِ الَّذِينَ يُقَاتِلُونَكُمْ وَلَا تَعْتَدُوا" ("Wa qātilū fī sabīlillāhi alladhīna yuqātilūnakum wa lā ta'tadū"), which translates as "fight in the way of Allah those who fight you, but do not transgress." The part usually left out when this verse gets quoted is exactly the second half: a permission with a limit written right next to it, not a blank cheque.
That, at bottom, is the difference between justice and revenge. Revenge wants the other person to suffer as much as we did, or more. Justice wants the situation corrected, and stops there. One has a defined limit, the other usually doesn't.
We see this on a small scale every day. Someone treats us badly and we want them to feel the same, multiplied. We call it justice, but sometimes it's just pride with a nicer name.
What's hard isn't deciding to respond to an injustice. It's deciding when to stop responding, especially while we still feel we're right. That takes more self-control than reacting does, and it's probably why we talk so much about justice and so little about its limits.
Do you really know how to recognize the moment justice already happened? Or do you keep asking for more anyway?