Question

Achilles' heel

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A∙chil∙les' heel / əˌkɪliz ˈhil ; əˌkɪli:z ˈhi:l /
◙noun [C]
1. a weak part of someone's character, which could cause them to fail at something
• 〔某人性格中的〕致命弱点，致命伤:
 »I think Frank's vanity is his Achilles' heel.
  我认为，虚荣心是弗兰克的致命弱点。