There are various synonyms for the phrase "make bitter." Some of the commonly used synonyms of this phrase include, embitter, sour, infuriate, dishearten, sour the mood, vex, resent, and poison. All these words signify the same meaning of turning a situation or an experience unpleasant or unsavory. For instance, embitter means to make someone feel resentful or bitter, while sour denotes an experience that has turned unpleasant or has spoiled the mood. Similarly, the word vex implies causing annoyance or irritation, and the word poison refers to a situation that has become corrupted or turned malicious. Overall, all these words are potent and useful in describing situations that have turned distasteful or unpleasant.