Meaning: vulnerability (definition and example).


Example: His lack of attention to detail was his Achilles’ heel.
Origins: Greek mythology. First cited in literature by Samuel Taylor Coleridge, 1810. (Source.)
Rewrites: Achilles’ weak spot Thor's mind Samson’s locks Kal-El’s kryptonite Spiderman’s Mary Jane Death Star’s thermal exhaust port

Discussion: Some of these you have to know the story to get the vulnerability and so they may not work as instantaneously as the original. Others may break through right away, depending on your audience.