Synonyms for Unrepentant (same or very similar meaning)
WordNet sense 1 (stubbornly persistent in wrongdoing):
obdurate, obstinate, cussedWordNet sense 2 (not reformed morally or spiritually):
unregenerate, unregeneratedWordNet sense 3 (not penitent or remorseful):
impenitent, unremorsefulFrom the ODE community, based on WordNetadd/edit