Which substance, when added in excess, would fully react with the acid without leaving an alkaline solution?

The question seems to be incomplete. To provide an accurate answer, I need to know which specific acid we are talking about. Different acids react differently with various substances. However, in general, a neutral substance or a base (also known as an alkali) can react with an acid. If the base is added in the exact amount needed to neutralize the acid, the solution will not be alkaline. If the base is added in excess, the solution will be alkaline. Therefore, to fully react with the acid without leaving an alkaline solution, the substance added must be in the exact amount needed for neutralization.