enormous, enormity

Enormous or enormous means very, very, large--
The blue whale is an enormous creature.
The new facility was built at an enormous expense.

Enormity or enormity means heinous or outrageous in character, or a heinous or horrible crime or act--
The public was shocked by the enormity of the crime.
The terrorists did not anticipate the strong public reaction to the enormity they committed.

Now that you know that, you can say--
"The enormity of the act of terrorism generated an enormous outpouring of public sympathy and support."

Note--"enormousness" is a noun ( thing or idea ) meaning the state or condition of being very, very, large--
The whale's enormousness, so close to the ship, left the passengers astonished.
"Enormously" means to a great extent or degree--
The investigators were sure that he had profited enormously from the deal.
Note--"enormity", along with "heinous", and some other words, can be used, unwittingly, to beggar the English language. You may find authors using these terms to describe crimes which are, unfortunately, all too common. "Enormity" and "heinous" should be reserved for a particularly shocking or outrageous crime or act, or we will have nothing left to describe such incidents.