Your reputation precedes you
What would you do if the tyrannical person of all time were standing in front of you? For instance, let’s say Genghis Khan was with you right now. We’d scream our lungs out and try to escape, not only because Genghis is back from the grave. “Unsettled” would describe anyone who had a fighting chance to defeat a supervillain.
In this scene, Director of Weapons Research, Orson Krennic, meets the 7-foot-tall space wizard in person. Vader seems surprised that Orson is unsettled by his appearance, somehow forgetting that his reputation would precede him. Anakin probably lost his sense of smell since he didn’t notice Orson had just spoiled his trousers.