supreme moment

supreme moment (plural supreme moments)

1. (often preceded by definite article) The point in time at which some astounding, significant, or life-changing event takes place.
   • 1913, Arthur Conan Doyle, “(please specify the page)”, in The Poison Belt […], London; New York, N.Y.: Hodder and Stoughton, →OCLC:

     "We have been together so many years. It would be sad to fall apart at the supreme moment."