Antonyms for the phrase "spares no effort" can be "lazy," "unmotivated," "apathetic," "indifferent," or "inactive." These words depict a lack of action, enthusiasm, or willingness to put in the extra effort required to accomplish a task. When one spares no effort, they go above and beyond to achieve their goals, whether it's through sheer determination or relentless hard work. In contrast, the antonyms of this phrase suggest a lack of interest or drive, hindering one's ability to achieve success. It is essential to stay motivated and dedicated to make progress and reach one's desired outcomes.