22lr or 22WMR out of a rifle. One shot with HP's usually does the trick. Same rounds in a pistol requires multiples unless you get excellent shot placement.
That said, my cousin in Texas likes a S&W 686, not much but the half shell left. Do not shoot from close up........
I took the top of one's head off with a 30 06 once at around 50 yards. Amazingly, he didn't die immediately. Bucked like a bronco for about 10 seconds.