Slit him up the belly and leave him to die in the gutter like the dog that he is. No sympathy.
Just shoot a blank up his "exhaust". That would tear him up a bit, and then leave him there.
Right on target, shall we say...
Shoot him? SHOOT HIM? What kind of insensitive, IRA supporting, conservative monster are you.
Castrate him with no anesthetic. Tie him naked to a rope with the other end tied to a camel and send it running through a cactus-covered desert at high noon. Cover his sorry a$$ with honey and stake him to the ground next to a mound of imported fire ants (import them if necessary). Take him out in the ocean, cover him with pigs blood, and dip him in the water to troll for sharks. Make him look at a slideshow of a swimming party with Hillary, Janet Reno and Madeline Albright in bikinis with his eyelids forced open a'la "A Clockwork Orange."
How could anyone in good conscience suggest anything as painless as shooting him. Sheesh!
Shalom.