A .45 is DEFINITELY better than nothing.
The MAJOR contributing factor is simple.
It depends if you hit a kill spot.
And it depends if the animal is fully enraged and charging at you.
I'll tell you right now, if you have a large cat or bear charging with full aggression, you might as well just jump head first right into their mouths!
Because i've seen and heard of persons emptying entire magazines into the animal and it didn't even stun them for a second.
Don't believe me?
The average person can literally be shot several times under full adrenaline rush and not even NOTICE until later!
(been documented by police and during war time)
Now imagine a 400lbs Cat or 800lbs Bear with an adrenaline surge.
You think they are going to feel anything?
Plus it's going to be a hell of a shot hitting an animal charging 30 or 40mph at you at close range. You will barely have time to react.
It will be in your face so fast.
Especially a cat, 99% of the time, you wont even see them, you'll be laying on the ground and seeing red in a split second.
If you actually have the opportunity to shoot at one, you can probably drop a cat with a kill shot, or firing several shots mid-body hopefully hitting a major organ. Aiming for the heat is a risky shot.
Especially with bears, there have been several reports of pistol rounds or smaller rounds purely DEFLECTING right off of a bears skull........of course were talking MASSIVE bears.
Their skulls are INCREDIBLY thick beyond belief.
Better off going with a straight body shot, your adrenaline will be going full speed and you CANNOT afford to miss a shot, so aim for something you can ACTUALLY hit in a realistic scenario.