Giving one all is an expression that means to give your maximum effort or to do everything in your power to accomplish a task or goal. Some antonyms for this phrase could be slacking off, half-heartedly attempting, or merely going through the motions. These actions convey neglect and indifference towards the task at hand. Giving superficially, only the bare minimum required, doing things half-heartedly, disinterest, apathy; all of these words are antonyms for giving one's all. On the other hand, the synonyms of giving one's all would be hard work, dedication, and perseverance. Therefore, the antonyms of giving one's all are the opposite of maximum effort and enthusiasm.