實用口語:如何說"致命弱點"

One's Achilles' heel（致命弱點）
    Weak or vulnerable point; fault, esp in sb's character, which can lead to his downfall.
    致命弱點；（尤指某人個性中可導致一敗涂地的）缺陷。
    關于Ahilles：
    【希神】阿基里斯（除腳踵外，渾身刀槍不入）
    When Ahilles was an infant, his mother tried to make him immortal by bathing him in a magical river.
    當阿基里斯還是嬰兒時，其母親為了使他永生而在神秘河里為他洗澡。
    請看例句：
    Vanity is his Achilles' heel.
    虛榮自負是他的致命傷。