What is relation between caliber of the ammunition and its lethality?

Answer 1

This is really a complication question, however here is a relatively short answer:

Caliber refers to the diameter of the bullet fired. If absolutely everything else is equal, a larger caliber will create a larger hole in the target. If the target is a living being/animal, a bigger hole will allow more blood to escape or will cause more damage to the tissue, causing quicker death or incapacitation. In other words, the bigger the hole, the more lethal the shot is likely to be.

However, the short version of the much longer answer is, there is much more to it than just that. Muzzle energy is a big part of it also, and a bullet with more muzzle energy will create more damage to the tissue. Also, a hollow point that expands and gets jagged will create more damage than the same size bullet that doesn't expand.

Also, it depends on what the bullet damages.

Lethality is basically a combination of those three things; how big the hole is, how much damage it causes, and what it damages. In other words, a .22 bullet directly to the heart is much more likely to be lethal than a .45 to the fat roll.