天tiān下xià无wú双shuāng

Literal: under heaven, without a pair
Figurative: Peerless, second to none; so outstanding that nothing else compares. Used of people, talents, products or places that are truly exceptional.

Where does 天下无双 come from?

The phrase is ancient and already appears in Sima Qian's 《史记》 of the Han dynasty. In the biography of Lord Xinling (Xìnlíng jūn) of the state of Wei, Lord Pingyuan says of him "my wife's younger brother, Lord Xinling, has no equal under heaven" (tiān xià wú shuāng), alluding to his fame and talent after exploits such as stealing the military tally to rescue the state of Zhao. Later the expression became famous in the saying "天下无双，江夏黄童," recorded in the 《后汉书》, which extolled Huang Xiang (Huáng Xiāng), a child prodigy from Jiangxia (in present-day Hubei) renowned for his literary gifts and filial devotion: as a young boy he fanned his father's sleeping mat cool in summer and warmed his quilt with his own body in winter. From there the idiom came to denote anyone who stands head and shoulders above the rest.

Source (出处): 《史记·魏公子列传》

How is 天下无双 used? Two examples

这zhè位wèi老lǎo师shī傅fu做zuò的de菜cài在zài我wǒ们men这zhè座zuò城chéng市shì可kě以yǐ说shuō是shì天tiān下xià无wú双shuāng。
The dishes this old master cooks could be called second to none in our whole city.
她tā的de画huà技jì天tiān下xià无wú双shuāng，很hěn多duō人rén专zhuān门mén来lái买mǎi她tā的de作zuò品pǐn。
Her painting skill is peerless, and many people come specially to buy her works.

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