Since Reddit is full of hypocritical people who are not properly educated on hunting and stuff back all kinds of meat from farm animals while they judge people who hunt naturally this will probably get me downvoted to hell but fuck it:

Large enough caliber to the chest will drop someone pretty quickly.

I don't know about people but I've made many perfect lung + heart shots with a 30-06 rifle on deer and it still takes them a couple minutes to die...

For this I probably deserve the downvotes, it still bothers me thinking about it, only mentioning it to warn other people and prevent it from happening to someone else: Birds are insanely resilient, I stopped taking any chances with ruffed grouse and cut off their head after I shoot them. I am a very humane hunter, I hunt strictly to feed myself and will only take a shot if it is a 100% guaranteed to be a clean kill. I took off half the head of a ruffed grouse last hunting season with my 12 gauge and tossed it on the floor in the back cab of my truck, about 30 minutes later I opened the door to put another one in and it jumped out of the truck and ran across the road into the bush and almost got away.. I felt absolutely horrible and now cut off their head no matter how dead I think they are. Poor thing was alive the entire time in the back listening to me and my buddy talking while driving down the hunting trail... My buddy is a zoologist and said with that much damage its nerves were shot / it had to be running on pure instinct and adrenaline / felt no pain, but still haunts me to this day.

If you hunt Ruffed or Spruce grouse (partridge) make sure they are dead as quickly as you can.