crown of thorns has 4 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.
any affliction that causes great suffering
“that is his cross to bear”
somewhat climbing bushy spurge of Madagascar having long woody spiny stems with few leaves and flowers with scarlet bracts
Synonyms, antonyms and the broader and narrower relations for crown of thorns come from Princeton University’s WordNet. Full sources and licences.
a mock crown made of thorn branches that Roman soldiers placed on Jesus before the Crucifixion