An antonym to "sprezzatura" from a Sherlock Holmes adventure:
""You remember," said he, "that some little time ago when I read you the passage in one of Poe's sketches in which a close reasoner follows the unspoken thoughts of his companion, you were inclined to treat the matter as a mere tour-de-force of the author. On my remarking that I was constantly in the habit of doing the same thing you expressed incredulity."

A "tour de force" is a master-stroke, a striking display of skill and power.