The phrase "most impelling" implies something that is very compelling or driving. To find its antonyms, we need words that have the opposite meaning. Some possible antonyms for "most impelling" include lethargic, unconvincing, unimpressive, unpersuasive, lackluster, weak, uninteresting, uninspired, or unstimulating. These words suggest a lack of intensity or energy and fail to inspire people or motivate them to action. People or things that are described by these words are less likely to capture people's attention or make them feel excited. When we want to emphasize the importance or urgency of something, we need to use strong, passionate, and persuasive words, not their antonyms.