reformation has 2 distinct synonyms spread across 2 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. 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.
improvement (or an intended improvement) in the existing form or condition of institutions or practices etc.; intended to make a striking change for the better in social or political or religious affairs
a religious movement of the 16th century that began as an attempt to reform the Roman Catholic Church and resulted in the creation of Protestant churches
rescuing from error and returning to a rightful course
“the reclamation of delinquent children”
Synonyms, antonyms and the broader and narrower relations for reformation come from Princeton University’s WordNet. Full sources and licences.