penalty has 3 distinct synonyms spread across 1 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 reward.
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 act of punishing
a payment required for not fulfilling a contract
the disadvantage or painful consequences of an action or condition
“neglected his health and paid the penalty”
(games) a handicap or disadvantage that is imposed on a competitor (or a team) for an infraction of the rules of the game
Synonyms, antonyms and the broader and narrower relations for penalty come from Princeton University’s WordNet. Full sources and licences.