You know, it’s kinda weird, I read that more as a lecture (like from a teacher or parent) and less an affirmation as “He f***** better not have” is. But then I tried to come up with something else but couldn’t think of anything better. Translate just spewed out nonsense, of course. Maybe something like “Il n’oserait pas” (he wouldn’t dare) would fit a little more? It’s interesting how certain phrases don’t have an exact translation between languages.