Most unrepenting means refusing to show remorse or regret. Some antonyms for this phrase could be contrite, regretful, apologetic, penitent, or remorseful. These words all convey a sense of admitting wrongdoing and feeling sorrowful for it. Contrite suggests a deep sense of guilt and remorse, while regretful implies a feeling of sadness and disappointment about an action taken. Apologetic and penitent both imply a desire to make amends for past mistakes. Lastly, remorseful conveys a sense of deep regret and a desire to make things right. By using these antonyms, writers can effectively convey the opposite of the phrase "most unrepenting.