The antonyms for "let off this time" include words like punish, penalize, discipline, rebuke, chastise, condemn, scold, and reprimand. These words convey a sense of taking responsibility for one's actions and facing the consequences of their behavior. While "letting off" someone suggests leniency, forgiveness or an opportunity to escape accountability, the antonyms represent a different approach. They send a message of accountability, personal responsibility, and the importance of learning from one's mistakes. In the end, choosing the right antonym depends on the context and the desired outcome, be it deterrence, rehabilitation, or simply making things right.