Could a girl beat a guy in a fight if she kicked/kneed him in the balls?
Most Helpful Guy
Could she? Yes. It's certainly a possibility.
A few things to consider:
1) You need a clean hit against a target most men are fairly good at insinctivly covering. How good is the girl at kicking strategically.
2) A groin kick isn't an instant win button. Even with a clean impact it'll take a lot of force to hurt a guy enough to stop him, and in certain mindets he still might just push through the pain.
3) What is the context of the fight. While an armed fight can often be won with speed, and skill is the most important factor, in a bare handed brawl strength and endurance provide the biggest advantages. Even an average guy is vastly stronger than a strong woman if he intends her harm.
Generally a solid kick to the groin, from a woman who knows how, and when, to kick, will buy her enough time to gain an uperhand in the situation and flee. But it won't instant win the fight, especially not if she is an ammateur and he isn't.2
Most Helpful Girl
I think winning a fight and doing just enough to get away are two very different things. I could never imagine doing this, unless I was about to get sexually assaulted or he was otherwise trying to physically abuse me or a family member, or in a life and death situation. As some of the guys said above, they have their whole lives have been instinctively training to protect that part of their body. In sports and in life, they automatically go to protect their most vulnerable area. So, for you to be fast and sneaky enough to have that work is slim. Even then, the guy will still be stronger and faster than you. I think instead of these things, invest in some pepper spray. That will take him down because he truly can't see you. Then run. Get to other people and get to safety.1