The word "worst" refers to the lowest or most inferior quality of something. Synonyms for "worst" include terms such as dreadful, terrible, and appalling, which all describe a negative scenario or situation. The phrase "the least favorable outcome" is also an excellent substitute for the word worst because it conveys the idea of something that is not desirable. Other common synonyms include inferior, lousy, mediocre, and substandard. If you're looking for a more severe term, you can consider using words such as abhorrent, atrocious, or execrable. Ultimately, the choice of word depends on the context of the situation where it is being used.