The phrase "beat one's breast" is an expression used to describe someone who is expressing vocal remorse or sorrow. The antonyms for this phrase could be a person who is stoic or indifferent, showing no remorse or guilt, or someone who is extroverted and boisterous, expressing their emotions in a very vocal and public manner. Other antonyms could include being apathetic, unfeeling, emotionless, or even robotic. The opposite of "beating one's breast" could also be someone who is experiencing joy, happiness, or contentment in a given situation rather than sorrow, regret, or guilt. Ultimately, the antonyms for this phrase represent a wide array of emotional states that contrast with the expression of remorse or sorrow.