Worst-case scenarios are situations that nobody wants to encounter as they often involve negative outcomes. However, it's important to have a backup plan in case something goes awry. Here are some synonyms for the term 'worst-case scenario' that can be used in your vocabulary: catastrophe, disaster, nightmare, calamity, apocalypse, tragedy, debacle, downfall, doomsday, Armageddon, cataclysm, fiasco, and crisis. By having these synonyms in your lexicon, you will be able to express yourself more effectively and sound more articulate when describing a potentially negative situation. It's always good to prepare for the worst but hope for the best.