If the offender has only ever committed one crime, and they did so while a teen, then OK. Give them another chance, provided they have a workable budget that includes a non-criminal job.
If the offender repeated the crime while being older than 25, then no. There is no realistic hope that the person will ever be non-harmful. Never let them free.
(cases between those two extremes are questionable)
I would be extremely wary of making such cosmological, sweeping generalisations about anything. "Realistic hope that the person will ever be non-harmful" really depends on a gazillion other variables.
And why start with a semantically negative presumption, anyway? A world of difference in attitude can be reaped from daring to ask whether a person might harm again, rather than if they will "ever be non-harmful".
You missed the word "repeated". Also, some participants in drunken fights act in self-defense or as part of a fighting sport, and so would not be criminals.
So it's actually like this:
You reach 25. You assault somebody. You serve time in prison. (now a questionable case) We decide to give you a second chance. You feel no need to follow the law, and you enjoy assaulting people, so you do it again. OK, at this point we know what kind of person you are. You didn't just make a bad decision one day. Simply letting you out into society is pretty much the same as assaulting a random person, because that is clearly what you are going to do.
If the offender repeated the crime while being older than 25, then no. There is no realistic hope that the person will ever be non-harmful. Never let them free.
(cases between those two extremes are questionable)