WordNet records no synonym and no antonym for scenario. 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.
an outline or synopsis of a play (or, by extension, of a literary work)
a setting for a work of art or literature
“the scenario is France during the Reign of Terror”
a postulated sequence of possible events
Synonyms, antonyms and the broader and narrower relations for scenario come from Princeton University’s WordNet. Full sources and licences.
“planners developed several scenarios in case of an attack”