hero has 19 distinct synonyms spread across 3 of its 7 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. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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 principal character in a play or movie or novel or poem
Greek mathematician and inventor who devised a way to determine the area of a triangle and who described various mechanical devices (first century)
(classical mythology) a being of great strength and courage celebrated for bold exploits; often the offspring of a mortal and a god
(Greek mythology) priestess of Aphrodite who killed herself when her lover Leander drowned while trying to swim the Hellespont to see her
a large sandwich made of a long crusty roll split lengthwise and filled with meats and cheese (and tomato and onion and lettuce and condiments); different names are used in different sections of the United States
Synonyms, antonyms and the broader and narrower relations for hero come from Princeton University’s WordNet. Full sources and licences.