The word "ungrudging" refers to someone or something that is generous, liberal, or willing to give without hesitation. Therefore, the antonyms for the word "most ungrudging" would be any word that denotes someone or something that is hesitant, stingy, selfish, or restrictive. Some of the possible antonyms for "most ungrudging" include reluctant, ungenerous, miserly, penny-pinching, selfish, and close-fisted. These words describe people or things that are not willing to give or share, and often hold back even when they could easily give more. Thus, when talking about something or someone that is not most ungrudging, we might use words like "least generous," or "most reluctant to share.