How about I offer an example? What if someone is, for instance, a serial killer who cannot be reasoned with? If cutting off their free will can save lives, wouldn't that be justified? Or what if someone is about to kill themselves? Wouldn't it make sense to take over for a moment, just to pull them back from the edge?

It depends on what type of fight, I think. If it is simply sparring, there are certain rules of conduct that are necessary to keep anyone from getting terribly hurt. If you in war and fighting for your life, then you are certainly allowed to try and save yourself with whatever resources you have. Torture and the like is often unnecessary, but when you are up against people that are trying to kill you, then there are many actions that are justifiable that ordinarily might be unacceptable.