Antonyms for the phrase "is of advantage" refer to things that are disadvantageous or harmful. Some words that could be used as antonyms include detrimental, harmful, disadvantageous, detrimental, unhelpful, unprofitable, harmful, and counterproductive. These antonyms imply that something will not result in a positive outcome, and may even lead to negative consequences. Using antonyms of "is of advantage" can express disagreement, criticism or a lack of support for a situation or decision. When making an argument, it's often helpful to use both sides of an issue, and antonyms provide an excellent tool for exploring the negative side of a topic.