unsympathetic has 6 distinct synonyms spread across 4 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. Its one recorded opposite is sympathetic.
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.
not sympathetic or disposed toward
“unsympathetic officialdom”
(of characters in literature or drama) tending to evoke antipathetic feelings
“all the characters were peculiarly unsympathetic”
not agreeing with your tastes or expectations
“found the task disagreeable and decided to abandon it”
Synonyms, antonyms and the broader and narrower relations for unsympathetic come from Princeton University’s WordNet. Full sources and licences.