renunciation has 6 distinct synonyms spread across 4 of its 4 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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.
rejecting or disowning or disclaiming as invalid
“Congressional repudiation of the treaty that the President had negotiated”
an act (spoken or written) declaring that something is surrendered or disowned
the act of renouncing; sacrificing or giving up or surrendering (a possession or right or title or privilege etc.)
Synonyms, antonyms and the broader and narrower relations for renunciation come from Princeton University’s WordNet. Full sources and licences.