To be two-faced; to act in a hypocritical or duplicitous manner, showing one attitude to someone's face and another behind their back.
他总是对领导阿谀奉承，背后却抱怨连连，真是个阴阳两面的人。
He always flatters the boss to his face but complains constantly behind his back; he is truly a two-faced person.
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