The phrase "most upper-crust" refers to individuals or groups at the highest social status, often associated with wealth, privilege, and exclusivity. However, antonyms for this phrase may include "most common", "most ordinary", "most average", "most humdrum", or "most working-class". These terms suggest a lack of sophistication, refinement, and elegance that are characteristic of the upper-class. Alternatively, "most egalitarian" or "most inclusive" could also be considered antonyms as they convey a sense of equal opportunity and lack of hierarchical social structures. Overall, the antonyms for "most upper-crust" emphasize the diversity and complexity of social stratification and challenge the notion of an exclusive elite.