I've oftentimes taught beginner students on self-defense.
Lesson #1 ~ You literally cannot defend your life without hurting your attacker. Physically impossible to do so. Doesn't matter if that attacker has two legs or four. A powerful light is useful for identifying something off in the distance or checking a long, straight trail at night. Just like a human-being, shinning a light in an animals face might cause it to stop and turn its head away for a split-second. But even a primitive animal has enough sense to keep its eyes closed and charge straight ahead at the last location it remembers it saw its target.
But after lesson #1, I tell any students who wish to leave; please do so now because I can't spend hours re-wiring their thought process after years or decades of that horribly ingrained belief. Wouldn't be fair to waste the time of the other students.
Whether it's a bullet to their gut or a blast of pepper spray to the eyes, either way; you're hurting that animal in order to stop its attack on you. As far as what's more humane, folks forget that individuals have ended up blind after taking a massive blast of pepper spray to the eyes. I mean permanently blind. Doesn't always happen. But happens enough. Personally, if that person who got blasted in the face was trying to kill or horribly injure another person; yeah not much sympathy from me.