罪魁禍首 [ㄗㄨㄟˋ ㄎㄨㄟˊ ㄏㄨㄛˋ ㄕㄡˇ; zui4 kui2 huo4 shou3] criminal ringleader, main offender (idiom); main culprit fig. main cause of a disaster ◄ ►