The phrase "with a bad grace" is often used to describe someone who is performing a task or doing something unpleasant in a begrudging and unenthusiastic way. Some common synonyms that can be used to describe this negative attitude include "half-heartedly," "reluctantly," "grudgingly," "unwillingly," "sulkily," and "resentfully." These words can help to convey the negative emotions and attitudes of someone who is not fully committed to a task or is unhappy about having to do it. By using these synonyms, you can paint a more vivid picture of the attitude and mindset of the person in question.