harsh has 3 distinct synonyms spread across 4 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. 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.
of textures that are rough to the touch or substances consisting of relatively large particles
“coarse meal”
sharply disagreeable; rigorous
“the harsh facts of court delays”
2 of the 6 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for harsh.
Synonyms, antonyms and the broader and narrower relations for harsh come from Princeton University’s WordNet. Full sources and licences.