Just wondering - can this be used in the same idiomatic way in English when you say "You will pay!" when you're angry and want to take revenge?
I certainly can't see why not, I probably would though that might be just me using anglicisms in my Welsh.
Would you use the formal version in this case or the informal, in your opinion? It would seem odd to me to have to use a polite way of saying this when I'm supposed to be demanding revenge from someone who's done me wrong.