CHINK IN ONE'S ARMOR

chink in one's armor: translation

a chink in one's armor

Fig. a special weakness that provides a means for attacking or impressing someone otherwise invulnerable. (Alludes to an opening in a suit of armor that allows a weapon to penetrate.) •

Jane's insecurity is the chink in her armor.

•

The boss seems mean, but the chink in his armor is that he is easily flattered.