WordNet records no synonym and no antonym for survivor guilt. It is the only member of its synset, 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 deep feeling of guilt often experienced by those who have survived some catastrophe that took the lives of many others; derives in part from a feeling that they did not do enough to save the others who perished and in part from feelings of being unworthy relative to those who died
“survivor guilt was first noted in those who survived the Holocaust”
Synonyms, antonyms and the broader and narrower relations for survivor guilt come from Princeton University’s WordNet. Full sources and licences.