I haven’t seen the movie, but in the book, absolutely fucking not. At one point he abuses two 10 year-olds and from that point there was precisely 0 empathy from me. Bad shit happened to him while incarcerated which is unfortunate, but a lot of other things that happened to him before the incarceration and after he was released were completely deserved.
Edit: To be clear, he did plenty of other bad shit, and I’m not comparing the things he did between themselves, that was just the tipping point for him becoming irredeemable to me. His age doesn’t make a difference to me.
Expanding a little on your point, I feel like a lot of people miss one of the themes of the book being “does forcing someone to be a good person by stripping them of their free will actually make them a good person?” I don’t think Alex ever really regretted what he did, it’s just for a short time he couldn’t do it anymore. Even after they reverse his treatment, he goes and forms another gang. iirc The only reason he even thinks about stopping is because the violence isn’t “fun” anymore. So yeah, not really a good guy.