remission has 7 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.
an abatement in intensity or degree (as in the manifestations of a disease)
“his cancer is in remission”
a payment of money sent to a person in another place
the act of absolving or remitting; formal redemption as pronounced by a priest in the sacrament of penance
Synonyms, antonyms and the broader and narrower relations for remission come from Princeton University’s WordNet. Full sources and licences.