stressed has 2 distinct synonyms spread across 2 of its 2 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 unstressed.
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.
suffering severe physical strain or distress
“he dropped out of the race, clearly distressed and having difficulty breathing”
bearing a stress or accent
“an iambic foot consists of an unstressed syllable followed by a stressed syllable as in `delay'”
Synonyms, antonyms and the broader and narrower relations for stressed come from Princeton University’s WordNet. Full sources and licences.