heel of the mythical Greek hero Achilles which is his only weak spot
Statue of Achilleas Thniskon (Dying Achilles) at the Corfu Achilleion.
An Achilles' heel (or Achilles heel) is a weakness despite overall strength, which can lead to downfall. While the mythological origin refers to a physical vulnerability, idiomatic references to other attributes or qualities that can lead to downfall are common.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).