The queestion is, how doeas Stevenson present Hyde as a frightening outsider in the novel as a whole?
My answer:
Hyde represents the subconsious side of Dr Jekyll's persona. This connects to the idea Stevenson supported about thee duality of a character.
He believed that our subconscious side is more primal and closer to nature, therefore he depicts Hyde in an non-human way, in fact he's often portrayed as an animal in various parts of the novella.
When Carew's murder his about to happen we see Hyde burst in an "ape like fury", in another scene, Utterson encounters Mr Hyde. As he pats on his shoulder we see Hyde "shrink back from him in an hissing intake of breath", once again a laguage representing animal features has bee used to reflect Hyde's actions.
This animalistic Representation of him suggests that htere is nothing human in him , therefore cannot be considered part of the society f the upper class. In this way he takes the role of a freightening outsider .
Furthermore, the idea of primal subconsciousness recalls the works and studies of Freud, a pioneer of psychoanalysis, who Stevendson happens to have a strong intrerest in the same subject. Perhaps Stevenson is trying to tell us that tha duality of a character lies under the polish ways of the Victorian society, just like it is represented by the character of Dr Jekyll.
Even so, Hyde is represented as a frightening outsider through hi appereance as well. We know that he is deformed - in a deep and sinister way. He walks with a limp and appears short. Looking at him evokes disgust and a sense of horror at anyone that faces him. Once again he's sdescribe as different, from any other character, which leads us to consider him far from normal, especially in his appereance.
During Victorian time deformities were seen as a mark of evil therefore connected to sin and abnormality. We see Hyde described as "having Satan's signature onto hi face" when Utterson recalls the image of him.
On a specific occasion we see Hyde represented as a social outsider. When Hyde is asking him about Dr Jekyll we see that Hyde doesn't ude a "fitting language" meaning that he dosesn't stick to the decorum and social rules imposed by the Victorian society. Something that is a sign of low class status and disrespect. In this way Hyde is portrayed as a social outcast.
Finally, I would like to mention that in the novel all the characters are upper-class gentlemen, all of them except for Mr Hyde.
We see him as an outsider also from a class point of view as he lives in the poor side of London, Soho.
Soho is an area afflicted by criminality, where low status and poor people lived and a place where "no gentlemen would have ventured".
Through this parallel the theme of duality is found in both the city and the main character of Dr Jekyll, and Stevenson is using Hyde to reflect the bad side of London.
Overall Hyde isn't constrained nor by the law nor by social standards of the time, this makes him a daunting outsider.