From the point of view of the werewolf, the silver bullet is far from having a positive connotation. What similarly idiomatic word or expression could be used to express something that brings about one's destruction in a very precise and effective –sort of perfect-storm– kind of way?
The context is a promising technology or product that failed due to unrelated and unexpected conditions and/or developments in the market (here there is no fault on the part of the market-player; it's just mere chance). I can imagine this extending perhaps to literary evil characters which had contrived a very clever way to become strong or invincible, but the archetypal weaker character exploits a weakness that the villain did not consider (here there is perhaps some fault/blame to be assigned).
Thanks in advance.