The Chinese idiom 罪魁祸首 (zuì kuí huò shǒu) is a four-character compound formed through parallel and reinforcing semantics, where each character contributes to the overall meaning of "chief culprit" or "prime offender." It is structured as two paired, synonymous couplets: "罪" (crime) and "祸" (disaster/misfortune) represent the harmful consequences, while "魁" (chief/leader) and "首" (head/chief) both denote the primary or leading figure. Thus, the compound literally and metaphorically means "the chief of crime and the head of disaster," combining to emphatically identify the main instigator or root cause of a serious problem.