Sure-enough is an informal phrase that refers to something that is true or genuine. The antonyms for sure-enough can vary depending on the context. In terms of doubt or uncertainty, the antonyms could be doubtful, uncertain, or unclear. In contrast, if the context is about something that is not genuine, then the antonyms could be fake, counterfeit, or bogus. The opposite of sure-enough may also depend on the degree of certainty. Instead of being completely sure, the antonyms could be skeptical or suspicious. Therefore, the antonyms for sure-enough can range from doubt and uncertainty to fakeness and suspicion.