Going out to dinner with my (now-ex) fiance (the alcoholic, violent one).
He'd demanded that I "dress up so you don't look like a ****ing boy for once", so I'd made an effort, and actually put on a little black dress. I don't do dresses, generally, but I loved that little black dress. It was a cheap New Look one, and it was perfect for me: sensible length, simple design, nothing fancy. It also had a zip at the front, running all the way from the neck to hem.
We go to the restaurant. Ex quickly gets drunk, as per usual. By the end of the main course, he is extremely drunk. He reaches over, grabs the dress's zip at my neck, and pulls it all the way down to the hem, sending the dress front flying open into two halves, and exposing my bra, my knickers, and all of me in between, to the entire restaurant (including one very startled waiter rounding the corner at precisely the wrong moment).
I have rarely felt so humiliated before or since.
In a doomed attempt to salvage my few remaining shreds of dignity, I hold the dress front together with my hands, charge off to the loos, shove the first cubicle door I see, and almost fall on top of a small (and surprised) OAP sitting on the throne who'd evidently neglected to lock herself in. Wonderful: not only am I an unwitting flasher, I'm very nearly an inadvertent pensioner-squisher, too.
When I finally manage to make my way back to the table - all other diners and the waiting staff studiously avoiding staring at me - Ex is still laughing. He found it hilarious. And continued to find it hilarious for years afterwards.
I never wore that dress again.