Well, a bang stick will kill it and tenderize it all in one shot. Any dive shop should carry them. A 6-8 foot long pole with a 10/12g shotgun shell blank at the business end, designed to concuss a shark. Doesn't shoot any bullets or slugs--just hits with concussion on contact.
Then there's the old two-buck machete, one chop behind the head
should be able to reach and severe the spine on most fish, if you don't mind having a sharp object near your legs.
Either way, I've always believed in a quick clean kill as being an obligation.