800-pound gorilla

noun2

1. •
   An entity that dominates its environment.

   • Q: Where does an 800-pound gorilla sleep? A: Wherever it wants!
   • Back then, the mayor was an 800-pound gorilla in this town.
2. •
   Something dangerous, menacing, or frightening that is obvious but not addressed.

   • The mayor's abuse of his power was an 800-pound gorilla in polite conversation.