WordNet records no synonym and no antonym for crisis. 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 unstable situation of extreme danger or difficulty
“they went bankrupt during the economic crisis”
a crucial stage or turning point in the course of something
“after the crisis the patient either dies or gets better”
Synonyms, antonyms and the broader and narrower relations for crisis come from Princeton University’s WordNet. Full sources and licences.