unbend has 6 distinct synonyms spread across 3 of its 6 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. Its one recorded opposite is bend.
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.
unfasten, as a sail, from a spar or a stay
Synonyms, antonyms and the broader and narrower relations for unbend come from Princeton University’s WordNet. Full sources and licences.
free from flexure
“unbend a bow”
release from mental strain, tension, or formality
“unbend the mind from absorbing too much information”