zayıf nokta, zaaf.

listen to the pronunciation of zayıf nokta, zaaf.
Türkçe - İngilizce
(deyim) Chink in the Armor
Achilles heel, weak point
(deyim) 1. An narrow opening and vunerable area in one's armor that the opponent will usually aim for. This term relies on "chink" in the sense of "a crack or gap," a meaning dating from about 1400 and used figuratively since the mid-1600s. 2. A figurative term for a one's weakness, largest flaw or their prevention of success

We would have aced this presentation if Leo wasn't in our group. He didn't study at all, he's the chink in the armor.