sharpness has 9 distinct synonyms spread across 6 of its 7 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 2 recorded opposites are dullness, softness.
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.
a quick and penetrating intelligence
“he argued with great acuteness”
the quality of being keenly and painfully felt
“the sharpness of her loss”
the quality of being sharp and clear
Synonyms, antonyms and the broader and narrower relations for sharpness come from Princeton University’s WordNet. Full sources and licences.