Quick fix: menstrual cramps.
And the best herb for killer cramps is ...
... angelica root (Angelica sp.), preferably recently dried. All angelicas work (even though I'm not sure about Chinese angelica (Angelica sinensis); that doesn't taste like your normal angelica, it tastes of smoked lovage).
Don't go digging wild angelicas unless you're certain of your botany. There's deadly umbellifer species out there, and some of them look very much like one or the other wild angelica.
Me, I use home-grown Angelica archangelica. Yes, there's Angelica sylvestris all over the place (and no deadly lookalikes once you know what water hemlock (Cicuta virosa) looks like), but hey, I have the archangelica in my garden anyway, I might as well use that. Especially as I get extra seedlings every now and then, when the mother plant manages to flower.
Another very good plant for killer cramps is sweet flag, Acorus calamus.
I use dried root of either. The dried angelica root gets weaker as it ages, the dried calamus root gets stronger. I've given a very small jar (30 ml) of dried root bits; when that cramp hits you don't mess around with making teas, you chew a bit of root. Relief is instant.
A herbalist might be able to help with the cause of those cramps, which would do away with the need for these herbs. But until you get around to visiting one: these herbs are extraordinary, although both taste vile.