What dismays Utterson about Mr. Hyde when he confronts him?

Mr. Hyde is both confrontational and unfriendly. Utterson is worried that Hyde might be planning something in regard to Jekyll's will. He is discomfitted by the man's replies and demeanor and sees him as the epitome of evil.

 The lawyer stood awhile when Mr. Hyde had left him, the picture of disquietude.  Then he began slowly to mount the street, pausing every step or two and putting his hand to his brow like a man in mental perplexity.  The problem he was thus debating as he walked, was one of a class that is rarely solved.  Mr. Hyde was pale and dwarfish, he gave an impression of deformity without any nameable malformation, he had a displeasing smile, he had borne himself to the lawyer with a sort of murderous mixture of timidity and boldness, and he spoke with a husky, whispering and somewhat broken voice; all these were points against him, but not all of these together could explain the hitherto unknown disgust, loathing and fear with which Mr. Utterson regarded him.  "There must be something else,"  said the perplexed gentleman.  "There is something more, if I could find a name for it.  God bless me, the man seems hardly human!  Something troglodytic, shall we say? or can it be the old story of Dr. Fell? or is it the mere radience of a foul soul that thus transpires through, and transfigures, its clay continent?  The last,I think; for, O my poor old Harry
Jekyll, if ever I read Satan's signature upon a face, it is on that of your new friend."