Have been there.
Ex-wife took a poke at me twice.
Both times, it was after I turned my back and she punched me in the back of the head.
First time I laughed, because she immediately started shaking her hand in pain.
Second time, a few months later, same exact scenario - having an argument, she started getting really heated, and I told her we weren't getting anywhere if she was going to say ugly things like she just had (she had said something terribly nasty about one of my family members, essentially that she was sorry that they hadn't died in a recent accident). Turned around to walk away again, and *thwack* right in the back of the head. She was *REALLY* mad, and even though she could see in my face that smacking me had pissed me off, she blew up: "What the **** are you gonna do, huh? WHAT THE **** ARE YOU GONNA DO? Go ahead, you know you want to! And even if you don't, I'm going to call the cops on you - and who do you think they're gonna believe?" Backstory - I am 6'0 and was ~210 at the time, first degree black belts in shotokan karate and judo, and was training Brazilian jiujitsu with some pro fighter buddies; she is 5'0 and ~90 pounds and couldn't hurt a fly. She was indeed correct - not a cop in this country that wouldn't cuff me if they showed up to the house and this little woman claimed abuse.
I got mad, not doubt, but more from the insult of being hit (esp. from behind) rather than any pain. I had laughed off the first one, but this one crossed the line. I grabbed her, picked her up in the air, walked over the sofa, sat down with her in a mildly tight hug and said "DON'T do that. Whatever else we fight about, you CANNOT do that. EVER." She screamed at me for about a minute or two, awful stuff, and she tried pinching my hands and arms to make me let go (I didn't budge), but after that she calmed down. Then she hit me with something even worse - "I'm so sorry, I wish I didn't do that. Maybe you should slap me or something when I get like that. I deserve it. Come on."
WHOA. Full stop.
All possible kink aside, it was highly disturbing to think she *wanted* me to hit her, for whatever twisted reason.
I did not, and I would not. EVER. Even if I weren't twice her size and reasonably highly trained.
We divorced fairly soon after, and that stuff was actually a primary element in the decision - I did not want to have children with someone so willing to use physical force when she get angry (which was often, sadly).