The phrase "haddest flash" can be described using various synonyms depending on the context. In the case of a sudden insight, it can be replaced with "epiphany," "revelation," or "enlightenment." For a brief moment of clarity during a difficult situation, "moment of realization" or "clarity" can be used. For a sudden outburst of emotion or anger, "eruption," "burst," or "spasm" can be suitable substitutes. And for a sudden idea or thought, "brainwave," "flash of inspiration," or "eureka moment" can be used. Regardless of the context, there are plenty of synonyms available to describe the concept of a "haddest flash".