图tú穷qióng匕bǐ见xiàn

Literal: the map unrolled, the dagger appears
Figurative: When the true, hidden intention is finally exposed at the very end; the secret plan or motive comes to light at the last moment.

Where does 图穷匕见 come from?

In the final years of the Warring States period, Prince Dan of Yan sent the brave Jing Ke to assassinate the king of Qin, the future First Emperor. To get close to him, Jing Ke arrived with two irresistible gifts: the head of the defected general Fan Wuqi and a map of the Dukang territory that Yan offered in surrender. Before the court, Jing Ke slowly unrolled the map until, at its very end, a poisoned dagger he had hidden inside was revealed. Jing Ke seized the dagger and lunged at the king, but the king dodged him and the attempt failed.

Source (出处): 《战国策·燕策》

How is 图穷匕见 used? Two examples

他tā先xiān说shuō要yào帮bāng我wǒ们men，结jié果guǒ图tú穷qióng匕bǐ见xiàn，原yuán来lái只zhǐ是shì想xiǎng骗piàn钱qián。
At first he said he wanted to help us, but in the end his true intent came out: he just wanted to swindle money.
谈tán判pàn到dào了le最zuì后hòu，对duì方fāng图tú穷qióng匕bǐ见xiàn，提tí出chū了le苛kē刻kè的de条tiáo件jiàn。
When the negotiation reached its end, the other side revealed its true intentions and put forward harsh conditions.

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