Unpowerful is a word used to describe someone or something that lacks strength or influence. To describe the opposite of unpowerful, we can use a range of antonyms which represent the exact opposite of this term. Some of the antonyms for unpowerful include robust, influential, commanding, mighty, vigorous, powerful, and strong. These words signify strength, force, or authority, which are the exact opposite of being unpowerful. In a sentence, one could say: "The organization was robust and influential while the previous one was unpowerful and lacked strength." Ultimately, using the appropriate antonym for unpowerful can effectively illustrate the point of the speaker or writer.