act in bad faith; an act of treachery; a betrayal; breach one’s faith; break faith with sb; betray one’s trust; breach of trust(/confidence/faith); go back on one’s word;faithless; in open perfidy;be perfidious (/trai torous/treacherous); faithless; play false (/foul);punic faith; a treason/……它～的进攻，撕毁了亲手签订的协议，暴露了自己的狰狞面目，从而陷入了空前孤立。(《敬爱的周总理我们永远怀念您》Ⅲ—98) …their perfidious attack on us and their tearing up of.the agreement they had signed had unmasked their vicious features and isolated them completely，…
背信弃义bei xin qi yi
go back on one’s commitment or scrap an agreement
背信弃义
break faith with sb; be perfidious;faithless;breach of faith;perfidy
背信弃义bèi xìn qì yì
不守信用和道义。break faith with sb., be perfidious, punic faith, act in bad faith