demerit has 1 distinct synonym spread across 1 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 merit.
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 mark against a person for misconduct or failure; usually given in school or armed forces
“ten demerits and he loses his privileges”
Synonyms, antonyms and the broader and narrower relations for demerit come from Princeton University’s WordNet. Full sources and licences.