This is going to get brutal, but I believe that if a person’s entire existence on earth harms other people, then the world would be better off without that person existing (i.e. life imprisonment or death).

In my opinion, a tyrant should be assassinated if they perpetrate crimes against humanity, crimes against their own people, and show no ability to ever step back from such horrific acts. It would have been wonderful if someone could have killed Hitler earlier on in his mad run of power.

This then gets to the utilitarian realm of discussion: does the well-being of many outweigh the death of one? If some world leader was about to launch a nuclear weapon, I would be happy to hear their life was immediately put to an end. I would “celebrate” that day for the rest of my life, and teach my kids about the moment.

At some point, we get to this notion of self defense. The individual has the right to self defense, and society has the right to “self defense”, essentially now through the justice systems of the world.

What I wonder is, what is the net value to society when people believe they "got revenge" on a criminal / "they got what they deserved" / some notion of "we are happy the wrongdoers are suffering"

I truly wonder myself if that type of thinking promotes a safer society with less harmful criminal acts. Of course we MUST balance this with the sense of rehabilitation and reduction in recidivism.

Personally I believe the justice system should strive to fully rehabilitate and integrate offenders into society whenever possible, but still punish those who committed atrocious acts like rape, murder, violent robbery or home invasion.