Dr. Henry Jekyll is a man with a deeply divided sense of his private self and public self. In his public persona, he is a benefactor, a doctor, a long-time and good friend, and a scholar. In his private persona he yearns for more liberty (defined as freedom from restraint, control, obligation, interference or restriction) to indulge in activities that would bring him reprimands or even public disgrace if his actions were to be known.
Utterson describes him as being about fifty years old; a large, tall man without facial hair ("smooth-faced"). He also says Jekyll is devoted to charities and to his religion.
Mr. Hyde is an individual with only one part to his nature: He is only self-serving and destructive, although there is a contradicting duality consisting of self-serving brutality coupled with self-serving fear. He has unwarranted anger. He is callous and indifferent to such an extent as to be violent in his loathing of the existence of others.
He has no conscience, so he can harm and murder without a pang of feeling or a flash of restraint. He is also imbued with fear of retribution because he fears being executed for the murder he committed so earnestly that he becomes as a weeping child. [This might present a bit of an inexplicable paradox between being brazenly brutal and yet tremblingly fearful if Stevenson had not introduced the duality of viciousness and fear in the incident with the little girl in the street.]
Those who have seen Hyde assert that they feel a deformity to his person or nature though they can't define a physical cause for it. Hyde inspires a raging feeling in people who have to deal with him for any reason. It's a point of debate as to whether Stevenson is suggesting by this reaction that a Hyde-like duality lurks just below the surface of everyone's character or whether he is suggesting that Hyde's inhumanity inspires humanely protective rage in those who possess humanity. The incident with the little girl might suggest the latter (second) suggestion.
Hyde has gnarled hands. He is so small in stature that when the transformation occurs turning Jekyll into Hyde, the clothes on Jekyll's body overwhelm Hyde. His face is unlike Jekyll's in all respects. He walks and acts with a vigorous speed and energy. All in all, Hyde presents a repulsive sight and persona.