ladder has 2 distinct synonyms spread across 2 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.
steps consisting of two parallel members connected by rungs; for climbing up or down
Synonyms, antonyms and the broader and narrower relations for ladder come from Princeton University’s WordNet. Full sources and licences.
ascending stages by which somebody or something can progress
“he climbed the career ladder”