Psychopathy and narcissism are psychological/emotional disabilities. They're the emotional equivalent of being born without a limb - or in congenital cases, without the brain structures needed for empathy and adult risk management.
I don't know what to do with these people. No one does.
I do know they're the single biggest threat to our future as a species, because if they get into positions of power they wreak havoc on unimaginable scales.
And even if they don't, they reliably leave a trail of wreckage behind them, because their relationships are defined by lies, gaslighting, and emotional and physical violence.
Unfortunately we have limited tools for diagnosis, so there's no way to know for sure if a problem teen can be rescued, or if they're guaranteed to become a problem adult.