"incredibly spectacular" is correct and usable in written English.
You can use it to emphasize how amazing something is. For example: "The show was an incredibly spectacular performance!".
Seattle locals love to talk about everything that makes their city so incredibly unique; spectacular mountain vistas, a city surrounded by water, and more than 200 breweries for a quaffing good vacation.
The incredibly inventive and spectacular New York-based performance artist Narcissister wowed the crowd on the opening night of the festival.
It's a full-scale, fabulously cast, incredibly moving, sung-through spectacular.
It's like the desert conservatory at Kew Gardens with the roof off, a collection of rare plants from Madagascar, Mexico, the Middle East and South America added to indigenous Moroccan species, and forms a spectacular and incredibly peaceful setting for this small hotel.
As another chance to vote looms, Powell said this week to be elected amid such spectacular indifference was "incredibly embarrassing".
Biographer Benoît Peeters opined that Tintin in the Congo was "nothing spectacular", with some "incredibly cumbersome" monologues, but he thought the illustrations "a bit more polished" than those in Land of the Soviets.
Although the spectacular golden-fronted bowerbird was incredibly rare overall, they were quite common here.
Among the most spectacular is Kauai with the incredibly crumpled mountain crags, fluted escarpments and vast green valleys of its northwest Napali coastline.
Besides incredibly fresh seafood, Hula's also offers a spectacular view of the famous Waikiki sunset.
