I once saw a 3000 lb Charolais bull shot dead with one shot from a 22-250.

This fall I made a perfect 70 yard shot through both lungs of a whitetail buck using a .280 Rem. The buck ran 300 yards with two shattered shoulder blades and no lungs.

I saw a small black bear shot three times perfectly with a .308 run uphill away over Vancouver Island old growth slash before keeling.

I have wounded several deer with shotguns and bows, to the point where I quit using them.

I have seen blacktail deer nearly decapitated by a .222

I have shot black bear, deer, coyotes, etc dead without a twitch using shotguns and rifles. Clean kills are -- to my dogmatic view -- the product of accurate shooting combined with suitable bullets, usually aimed at a nerve. There are mathematics in play with distance shooting but killing to 'modern standards' usually seems to be a euphemism for 'making up for impatient and uneducated or otherwise innapropriate shots resulting in wounded animals'.

I killed my first deer at 14 with a .270 in one shot. I would shoot a moose with a .270 but only through the neck within 75 yards. But that's me. I try to shoot everything in the neck.