后hòu来lái居jū上shàng

Literal: the later arrival ends up on top
Figurative: When the one who started later, or from further back, ends up overtaking the front-runners; today it's usually admiring, though it began as a complaint.

Where does 后来居上 come from?

Ji An, an upright and sharp-tongued official under Emperor Wu of the Han dynasty, watched men who had entered the court after him receive posts above his own. As the 《史记》 tells it in his biography, he said so to the emperor's face: you use your ministers the way one stacks firewood, and the logs thrown on last end up on top. It was a complaint about treatment he considered unfair. Over time the idiom flipped its charge, and today it is mostly admiring, said of someone who started late or from behind and finishes ahead of the front-runners.

Source (出处): 《史记·汲郑列传》

How is 后来居上 used? Two examples

这zhè家jiā新xīn公gōng司sī后hòu来lái居jū上shàng，去qù年nián销xiāo量liàng已yǐ经jīng排pái到dào第dì一yī。
This newcomer has overtaken everyone; last year it already ranked first in sales.
他tā入rù学xué时shí成chéng绩jì一yī般bān，后hòu来lái居jū上shàng，考kǎo进jìn了le最zuì好hǎo的de学xué校xiào。
His grades were nothing special when he started, but he pulled ahead and got into the best school.

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