Oh hell I am glad MLA picked up on this kick him in the balls thing, or I would have.
Best case scenario, all works and you have your prey cough up his own testicles, and sink down into a pained whimpering heap, screaming silently.
Chances are actually rather better that you will connect awkwardly and instinct with have them bring their legs together and have you with a trapped leg and off balance and with arm's reach, missing completely and landing on your arse, or kicking their leg and upsetting them.
Bad call all around.
There are some things that are rather painful that do not involve exposing yourself to unbalancing yourself.
Finger up their nostril hard (or keys up the nostril).
Thumbnail in the eyesocket
Palms simultaneous clapped against their ears forcing air down their ear canal.
Stamping a heel against the base of their toes
A Blow to their Adam's apple
A Fish hook to the mouth.
Running the inside of your shoe down their shin.
Grab their balls in your hands, squeeze, twist and pull down hard in one hard movement
Now before you say "Fuck Les, you are a dirty fighter." I personally have done none of these things BUT if I was to give a preferred method to ladies of dealing with an attacker, than to "kick them in the balls" this would be my advice.
Advice for blokes would be a little different. Would go something like this.
Fucking dominate them. You do not have to physically hurt someone that much usually to cow them. To make them "fear" what they have got into and worry about what could happen. Have them believe that they are so far past the point of getting the upperhand that they are panicked and unable to put up a defence and are looking for an "out".
Go in hard.
Be mentally prepared for a flogging. If you REALLY want this fight and feel strongly enough to defend whatever reason you were fighting then you should be prepared to lose and cop a hiding, and once you have this set in your mind then go for the upside.
Don't back down unless you absolutely have to.
Protect your face, a smack to the cheek will hurt but won't fuck your chances as much as a belt to the nose. Your eyes willi water with this and for a five seconds you will be fucked and at their disposal.
Keep your guard up and elbows locked.
Keep your balance and do not charge in head down
Keep kicks to a minimum.
Don't allow them to hit you before you hit back. May be very gracious but when they are doing a bit of folk-dancing on your rib cage you won't thank them and they won't appreciate your goodwill.
Don't wait for the "perfect opportunity " or the "knock out punch". Go in quick flurries and hope that it will open up opportunities.
Don't be fancy
Don't wear yourself out faster than them.
Don't let them dictate how the fight is going or they will be the ones who will be dominating you in the end.
Only follow up as much as you need to, to win. If they are unconscious, stop. If they are calling it quits, stop. If they are no longer able to defend themselves stop (and back away from them enough to prevent them having been just playing possum). If they are bleeding? Who gives a fuck?
If you have really fucked them up and you are worried they are seriously hurt? Depends on the situation. Generally I would say "fuck it". (I have had a situation where I have had to get a towel and compress the arsehole's noggin from bleeding everywhere after his head split hitting the ground, but it would again depend on the situation. Generally I would say not to bother.)