badness has 5 distinct synonyms spread across 3 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 goodness.
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.
that which is below standard or expectations as of ethics or decency
“take the bad with the good”
Synonyms, antonyms and the broader and narrower relations for badness come from Princeton University’s WordNet. Full sources and licences.
used of the degree of something undesirable e.g. pain or weather
an attribute of mischievous children