Having a big bust answered itself, any women who fight be a real street fight or arranged matches will tell you first thing that your rival/opponent goes after is hair linger the hair the easier to grab, this why more than not you see us pin it up, tie it up, so on so yes big boobs sticking out are a prime target, a solid punch to the boobs hurts , grabbing on and twisting or crushing not much less pain, if you saw or head a woman was thrown by her boobs more likely the woman she was fighting went to rip her top realized she had breast meat , bra and the top and flung her, did hurt? I would say yes but a fight stopper ? Very doubtful I been grabbed at the boobs , scratched, punched, and bitten there , you have to account for Adrenalin fear and anger when pondering these questions then add in the fact everyone has different thresholds of pain level what might make 1 woman drop to knees might make a another pissed off