crowning touch

A final flourish, detail, or addition that adds extravagance or excellence to someone or something. The sign, a beautiful piece crafted by dozens of local artists, will be the crowning touch on the newly renovated museum. And finally, the crowning touch to your outfit—a pink feather boa! A: "Mom, I can't wear your diamond earrings." B: "Yes, you can—you know they would be the crowing touch with your wedding gown."