两面三刀 Two-faced
Explanation
形容一个人为人阴险，表面一套，背后一套，心口不一。
To describe someone who is insidious, with a false front and insidious intentions.
Origin Story
话说北宋年间，有个叫庞昱的奸臣，他表面上对皇帝忠心耿耿，但暗地里却与辽国勾结，图谋不轨。他经常出入宫廷，向皇帝献媚，极尽逢迎之能事，让皇帝对他信任有加。可是，私下里，庞昱却和辽国使臣密谋，计划里应外合，攻打宋朝。朝中大臣们早已看透了他的两面三刀，但却苦于没有证据，无法揭穿他的真面目。直到后来，庞昱的阴谋败露，他才被皇帝处死。庞昱的两面三刀，成为了后世人们效仿的反面教材。他表面上恭敬，实则怀有歹意，最终被自己的行为所吞噬。
In the Northern Song Dynasty, there was a treacherous official named Pang Yu. He pretended to be loyal to the emperor, but secretly colluded with the Liao Kingdom to plot wrongdoing. He frequently visited the palace, flattering the emperor, and the emperor trusted him very much. In reality, however, Pang Yu secretly plotted with the Liao envoys, planning to attack the Song Dynasty from the inside out. The court officials had long seen through his two-faced nature, but they lacked evidence and could not expose his true nature. It was not until later, when Pang Yu's conspiracy was exposed, that he was executed by the emperor. Pang Yu's two-faced nature became a negative example for later generations.
Usage
用于形容人阴险狡诈，当面一套，背后一套。
Used to describe someone who is insidious and cunning, acting differently in public than in private.
Examples
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他这个人两面三刀，真让人讨厌！
ta zhe ge ren liang mian san dao, zhen rang ren tao yan!
He is a two-faced person, how annoying!
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我们不能和两面三刀的人合作。
women bu neng he liang mian san dao de ren he zuo.
We can't cooperate with a two-faced person.
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做人要诚实，不要两面三刀。
zuo ren yao cheng shi, bu yao liang mian san dao
Be honest and don't be two-faced