It's ok to kill them as long as it doesn't hurt them too bad.
Hollow points were banned by a Geneva Convention treaty long ago because of the damage they cause. Sharp edged bayonets are banned for the same reason – they can have a sharp point but the edge must be blunt. Fortunately the bayonet issue is known by few people so that issue doesn’t come up.
I personally think the hollow point is more humane – let the guy bleed out instead of suffering.