喻本性难改。-----------------国语辞典:(谚语)比喻恶习不改,劣性难移。如:「他这个人没救了!真是狗改不了吃屎!」英语 lit. a dog can't stop himself from eating shit (idiom), fig. bad habits are hard to change
◎ 狗彘不若 gǒuzhì-bùruò[be more worthiless than pigs] 彘:猪。连猪狗都不如。比喻品行极端卑劣人也,忧忘其身,内忘其亲,上忘其君,则是人也而曾狗彘之不若也。——《荀子·荣辱》-----------------国语辞典:连猪狗都不如。比喻人品低劣。《荀子.荣辱》:「人也,忧忘其身,内忘其亲,上忘其君,则是人也,而曾狗彘之不若也。」《封神演义.第六二回》:「朝廷拜你为大将,宠任非轻,不思报本,一旦投降叛逆,真狗彘不若!」近猪狗不如反超凡入圣