culminate has 1 distinct synonym spread across 1 of its 5 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.
bring to a head or to the highest point
“Seurat culminated pointillism”
Synonyms, antonyms and the broader and narrower relations for culminate come from Princeton University’s WordNet. Full sources and licences.
reach the highest or most decisive point
reach the highest altitude or the meridian, of a celestial body
rise to, or form, a summit
“The helmet culminated in a crest”