Repaying a grievance with a straight line
It's a Chinese idiom. Pinyin is y à zh í B à oyu à n, which means to treat people who resent fairly. It comes from the Analects of Confucius.
The origin of Idioms
In the Analects of Confucius, Xian Wen: "to repay resentment with uprightness, to repay virtue with virtue."
Idiom usage
It refers to the attitude towards people. example it's called repaying one's grievance with one's uprightness and repaying one's virtue with one's virtue. Feng Menglong's a warning to the world in Ming Dynasty (Volume 11)
Repaying a grievance with a straight line
Cool breeze at the end of the day - tiān mò liáng fēng
mastermind with painstaking effort - kǔ xīn jīng yíng