The phrase "as frightful" is correct and usable in written English.
It can be used to compare something to another thing that is frightening or alarming.
Example: "The storm was as frightful as the tales of old sailors lost at sea."
Alternatives: "just as terrifying" or "equally alarming".
Playing the game was as frightful as it was fun.
This comparison is always as frightful as it is useless.
Oh the weather outside isn't nearly as frightful as the shitstorm inside this house.
His lawyer, Joseph A. Hanshe, described his client as "frightful about what was going on". "Right now, he has denied everything," Mr. Hanshe said.
Though Jonathan Pryce isn't as frightful looking as Wroe is described in the book ("small, dark and hunchbacked"), he skillfully conveys what made Wroe repugnant and charismatic.
If ever the world needed a symbol of the potency of the threat that confronts us all, here it was as frightful actuality.
He suggests: "open your being to experience--as challenging and frightful as that may be--and let that experience guide you in a direction that makes you feel comfortable in your skin.
Wodehouse: Stiff Upper Lip, Jeeves, read by Simon Callow (Penguin £8.99) Bertie Wooster finds himself as house guest at frightful Totleigh Towers, where lurks Madeline, a 'cross between a ticking bomb and a poltergeist', planning to enmesh him when her engagement to Gussie Fink-Nottle fizzles out.
Angelo and Isabella, Isabella and Claudio are locked in relationships as logical and frightful as those of historical revenge-tragedy; yet what Angelo says is merely, "Plainly conceive I love you".
But not even Hieronymus Bosch could have anticipated an angle as original and frightful as Hayes'.
Good old video ref. For the English, the whole experience came as a frightful shock.
