To cook the dog after it kills the rabbits
This refers to when someone casts aside or even kills the person(s) who helped them accomplish a task
Negative
如果事成之后，兔死狗烹，那将没有人敢跟他合作 | Rúguǒ shì chéng zhīhòu, tùsǐgǒupēng, nà jiāng méiyǒu rén gǎn gēn tā hézuò
If after the task is finished he gets rid of those who helped him, no one will dare to work for him
[Source]
在封建社会里，许多为统治阶级效力的人，最终落了兔死狗烹的下场 | Zài fēngjiàn shèhuì lǐ, xǔduō wèi tǒngzhì jiējí xiàolì de rén, zuìzhōng luò le tùsǐgǒupēng de xiàchǎng
In feudal societies, many who provided services to the ruling classes found themselves cast aside or eliminated in the end
[Source]
None
None
You can read about what the king had to endure as a captive in 吴国 (Wú Guó) in a related chengyu, 卧薪尝胆 (wò xīn cháng dǎn)
《韩非子》(Hán Fēi Zǐ), a book of philosophy authored by 韩非 (Hán Fēi) during the Warring States Period (475 - 220 BC)
During the Spring and Autumn Period (春秋时期, 770 - 476 BC), the two kingdoms of 越国 (Yuè Guó) and 吴国 (Wú Guó) often went to war with one another.
During the reign of the 越国 king Gōu Jiàn (越王勾践, Yuè Wáng Gōu Jiàn), 吴国 managed to launch an attack so devastating that 勾践 was captured, brought back to 吴国, and forced to do manual labor. However, following the advice of the senior official 范蠡 (Fàn Lí), 勾践 gained the trust of his captors, and years later, he was able to return to 越国. Then, with the assistance of 范蠡 and another advisor, 文种 (Wén Zhǒng), 勾践 was able to bring 越国 to power once more and defeat 吴国.
For his role in helping 勾践 regain power, 范蠡 was offered handsome rewards, but he did not take them. Instead, he resigned from public service and went to live a humble life.
The decision to live a humble life, however, was a calculated one, and 范蠡 wanted 文种 to take the same path as him. He wrote a letter to his friend, indicating that he suspected the king would be the kind of person who would share his troubles but not his triumphs, including the line 兔死狗烹 to emphasize the danger 文种 was in.
However, 文种 didn't believe that the king would harm him, and he stayed by the king's side. Unfortunately for him, a few years later, the king ordered him to kill himself, and 文种 had no choice but to comply.