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.
kryptoniteandAchilles Heel, I would go with the latter. This is becausekryptoniteis often used facetiously or in hyperbole for things that compulsively trigger people due to the fact that they really enjoy or obsess over it. I don't recall any humorous quips about chocolate ice cream being someone's Achilles heel -- the opposite, more or less a common occurrence. – kayleeFrye_onDeck Dec 14 '16 at 23:25