avatar has 2 distinct synonyms 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. 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.
a new personification of a familiar idea
“the embodiment of hope”
the manifestation of a Hindu deity (especially Vishnu) in human or superhuman or animal form
“some Hindus consider Krishna to be an avatar of the god Vishnu”
Synonyms, antonyms and the broader and narrower relations for avatar come from Princeton University’s WordNet. Full sources and licences.