Based on the very little bit I have seen here, I have a couple thoughts. One is that in general, if a 16 year old (or any minor) commits a crime and isn't put on trial for it until after their 18th birthday, they should not be exposed to any harsher penalties than they would have been subject to when they were a minor and actually committed the crime. Second is, this dude did a bad thing and definitely should see consequences for that. And obviously it wasn't a one-and-done thing, because he got busted for a DDoS attack too, and who even knows what else he got away with before he got caught on these things he's been held accountable for.
When you break the law, there are consequences. And when you do it internationally, even more so. But the consequences for the things he did as a 14-16 year old should be the consequences that would normally be issued to a 14-16 year old committing those crimes, not the consequences for an adult that did those crimes.