unregenerate has 4 distinct synonyms spread across 3 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is regenerate.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
not reformed morally or spiritually
“unregenerate human nature”
unrepentant and incapable of being reformed
“an unregenerate criminal”
Synonyms, antonyms and the broader and narrower relations for unregenerate come from Princeton University’s WordNet. Full sources and licences.