The phrase "let off the hook" means to release someone from a responsibility or obligation. Antonyms for this phrase include "hold accountable," "blame," "charge," "punish," and "penalize." These words imply holding a person responsible for their actions and not letting them escape consequences. In contrast to "let off the hook," these antonyms suggest holding someone accountable for their actions and ensuring that they take responsibility for their behavior. When someone is held accountable, they are likely to become more self-aware and less likely to repeat the same mistakes in the future. In summary, the antonyms of "let off the hook" suggest taking responsibility and holding individuals accountable for their actions.