original sin has no recorded synonym. 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 actual sin.
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.
a sin said to be inherited by all descendants of Adam
“Adam and Eve committed the original sin when they ate the forbidden fruit in the Garden of Eden”
Synonyms, antonyms and the broader and narrower relations for original sin come from Princeton University’s WordNet. Full sources and licences.