justice has 6 distinct synonyms spread across 3 of its 4 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 injustice.
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 quality of being just or fair
Synonyms, antonyms and the broader and narrower relations for justice come from Princeton University’s WordNet. Full sources and licences.
judgment involved in the determination of rights and the assignment of rewards and punishments
a public official authorized to decide questions brought before a court of justice
the United States federal department responsible for enforcing federal laws (including the enforcement of all civil rights legislation); created in 1870