The phrase "hammer out deal" typically means to negotiate and produce an agreement. Its antonyms, therefore, would be words or expressions that communicate the opposite meaning. For instance, rather than hammering out a deal, one might decide to break off discussions or refuse to come to terms with the other party. Other antonyms for this phrase might include words such as decline, dismiss, veto, or disregard. Alternatively, one could adopt a more passive approach and simply avoid negotiations altogether, choosing instead to remain aloof or distant from any potential deal-making scenarios. Ultimately, the antonyms for "hammer out deal" will depend on the context and purpose of the negotiation in question.