Rarely does a bloody nose get the job done.
What does work is to end the fight by destroying their mind, crushing their spirit, inflicting injuries that ensure perpetual physical pain, and leaving them alive, forever frightened of the next terrifying blow, as a reminder to all the other would-be bullies.
Never start a fight. But if forced to fight ensure you have the knowledge, tools, and most importantly, will, to beat your opponent to the point they think they are going to die, and then to the point where they are afraid they will live. At that point, the fight is over, and the threat is neutralized.
You are quite correct.
Machiavelli put it this way, “If an injury is to be inflicted on an enemy, it is to be so severe, that the enemy’s retaliation need not be feared.”