Mine was a long black cardigan I was knitting for a DSis. I’d made the whole thing - except for the very long ‘pick up and knit’ band that went all the way round.
It was horrendous, just trying to see the black stitches, let alone pick up the right number.
I just ditched the whole thing - just as well it was relatively cheap acrylic yarn - couldn’t be pure wool, she’d never hand wash anything.
Touch wood, that was years ago now and I haven’t had a UFO since, but there were a couple of smaller ones before that.