I don't think there is much hope for this kid in society. Anyone who would punch another person possibly to death has shown they are a total menace. It wouldn't bother me at all if he spends his life until his 40s in prison, and hopefully by then all the testosterone will be out of his system and maybe then he'll be less of a danger to society.
I've punched people in the head on about a dozen different occasions...as a juvenile. I've never punched another person as an adult. I disagree that it is a clear sign that this kid is a worthless human being.
People are not clockwork organisms, afterall.