softness has 13 distinct synonyms spread across 5 of its 10 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 3 recorded opposites are hardness, loudness, sharpness.
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.
the property of giving little resistance to pressure and being easily cut or molded
poor physical condition; being out of shape or out of condition (as from a life of ease and luxury)
a state of declining economic condition
“orders have recently picked up after a period of extreme softness”
a sound property that is free from loudness or stridency
“and in softness almost beyond hearing”
a visual property that is subdued and free from brilliance or glare
“the softness of the morning sky”
acting in a manner that is gentle and mild and even-tempered
“his fingers have learned gentleness”
the quality of being indistinct and without sharp outlines
the trait of being effeminate (derogatory of a man)
“the students associated science with masculinity and arts with effeminacy”
a disposition to be lenient in judging others
“softness is not something permitted of good leaders”
Synonyms, antonyms and the broader and narrower relations for softness come from Princeton University’s WordNet. Full sources and licences.