WordNet records no synonym and no antonym for fatalism. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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 submissive mental attitude resulting from acceptance of the doctrine that everything that happens is predetermined and inevitable
a philosophical doctrine holding that all events are predetermined in advance for all time and human beings are powerless to change them
Synonyms, antonyms and the broader and narrower relations for fatalism come from Princeton University’s WordNet. Full sources and licences.