chink in armor

chink in (one's) armor

A minor but very detrimental flaw or weakness. Yeah, he's brilliant, but his violent temper has destroyed many business relationships—it's really the chink in his armor.
See also: armor, chink

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.
See also: armor, chink