Revenge as a concept is basically justice, but perverted. Justice is typically based upon retribution, however over time people realized that’s a poor principle to base Justice entirely on.
Revenge becomes an issue when it becomes a blood feud or vendetta. Typically revenge killings are the norm in a lot of the world, but it always depends on for what? The Bible, Hammurabi’s Code, and a lot of Ancient Law/ Religious Texts detail fines and damages for murder/ accidental death or maiming.
Western Society really gives favor to the accused, very much in the US where intent and finding intent is most of the case. The issue comes in when society forces people to forgive (and later pay to keep them alive in prison.)
Fuck, I think life in prison is cruel. If a guy kills more than 3 people and went in with intent to kill or willfully endangered people like during a robbery than yeah, fuck ‘em. Shit like a Revenge Killing for shit like the Hi-Fi Killings, Junko Furata, Spree killer mass shooters, or serial rapists is a case where I can see it as actual Justice.
Revenge is bad, but people taking the law into their own hands is really flawed. I think it’s pussy shit to not fight for yourself. Forgiveness is for the ignorant, not the scared.
EDIT: Darrell Brooks should of just been executed after the trial. That dude is the ideal for a death penalty. Just an unrepentant asshole more worried about himself than those he wronged.