. Even being just an Air rifle - a .177 hunting pellet traveling at 1200 FPS can be one power horse.
These are rifle velocities that are being quoted....air pistols are somewhat less, especially in .177.
Suggestion.....for hunting....think big. Bigger is better in the air rifle and pistol realm. The .177s have higher velocity figures but the pellets have little mass and shed energy rapidly. The larger calibers may move more slowly but are carrying more weight and hold their energy longer. Benjamin, Air Force, and Evanix all make air pistols that produce impressive figures.....they are to be had in .22 (Benjamin and Evanix) and .25 (Air Force @ 55 ft.lbs. ME)
The .177 rifles can be had to better than 1400 fps. Zippy, no doubt. I wonder what pellet was used. Often the hi-vel stats are the result of using very light pellets like the 5.4 grain Gamo Raptor. At that velocity, a five grain pellet produces 25 ft.lbs of ME. A more normal 8 grain pellet at 1200 makes the same stat.
Move up to .22s and take a average 14 grain pellet move it at 1000 fps and the yield is 31 ft lbs and a larger hole. The big 28 gr Eu Jin pellets only have to move at 700 fps to do the same.
Move up to the big bores.......9mm and .45..... And velocities drop to 600 to 800 fps. Big holes, though, and well over 100 ft.lbs. (a .458 200 grain LSWC @ 600 fps is at 160 ft.lbs at and a hole that is more than six times the size of the .177)
Of course, you still have to place your shots properly no matter how big the hole.