When they finally meet, what is Utterson's reaction to Hyde?
Spotting Mr. Hyde down the street, walking toward him, Mr. Utterson felt that the man "went somehow strongly against [his] inclination"; in other words, Hyde inspires a dislike in others even from a distance. Utterson asks to see Hyde's face, so that he will know him in future, and Hyde mentions that it is actually a good thing that they should know each other. Utterson wonders if he is aware of Dr. Jekyll's will, which leaves all to Hyde should Jekyll ever disappear unaccountably. After their interaction, Utterson feels "disquietude" and "perplexity": he is unsettled and confused by Hyde's manner and person. 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 Mt. Utterson regarded him.
In short, despite Hyde's obvious flaws, Utterson is at a loss for how to account for his total aversion to the man, and he eventually decides that "'if ever [he] read Satan's signature upon a face, it is on that of [Jekyll's] new friend.'" He believes that Hyde is composed, then, of pure evil.
When Utterson meets Hyde in Chapter 2, Utterson is completely repelled by Hyde. His reaction to Hyde can be fairly neatly summed up in one line that Utterson speaks. He says to himself
God bless me, the man seems hardly human!
and then goes on to say
...oh, my poor old Harry Jekyll, if ever I read Satan’s signature on a face, it is on that of your new friend.
Utterson cannot really understand why it is that he dislikes Hyde and is so repelled by him. He thinks about how Hyde looks a little bit strange and about how Hyde sounds strange. But he thinks that these things are not enough to account for how deeply disgusted he is by Hyde. He wonders if he just hates Hyde for no good reason.
Utterson does not realize it at this point, but what he is seeing (and being repelled by) is the fact that Hyde is purely evil.