Originally Posted by
Mirage
Strikes to the throat, temples and back of the head are pretty lethal, especially if you do it over and over again. There's a reason why the most damaging strikes are banned in all combat sports.
Also keep in mind that defeating an enemy doesn't require you to kill them right then an there. Breaking someone's spine is going to prevent them from doing much of anything. Enough pain can make an enemy unable to continue too, and then you're free to finish them off in any way you desire. Most monsters still breathe air, so you could just strangle them, or cut off blood supply to the brain.
You can't prepare for every strike. There is no muscle you can flex to avoid getting knocked out, for example. Repeated strikes to muscle tissue make the muscles cramp up, reducing mobility and therefore also ability to avoid attacks.