responsive has 2 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. Its one recorded opposite is unresponsive.
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.
readily reacting or replying to people or events or stimuli; showing emotion
“children are often the quickest and most responsive members of the audience”
reacting to a stimulus
“the skin of old persons is less reactive than that of younger persons”
Synonyms, antonyms and the broader and narrower relations for responsive come from Princeton University’s WordNet. Full sources and licences.