Jabez Wilson is also a widower and pawnbroker. He isn't a very bright man, but he does love money, allowing him to be used by Clay as part of a scheme to rob a bank. He tries to get something for nothing two times during the story.
John Clay is a criminal who has eluded the police for years. Holmes considers him to be intelligent. We know he comes from royal blood, has had an aristocratic education, and is egotistical about his abilities as a criminal. This makes us think Clay gets involved with crime for the challenge of the game and not just for the money. He is imaginative and a formidable opponent for Holmes. He and Holmes are alike in many ways except when it comes to their motives and the morality of their actions.
Sherlock Holmes is known for his ability to tell a great deal about a person by observing his/her little idiosyncracies. He's very intelligent and has knowledge about insignificant topics and previous criminal cases. He no doubt gets pleasure from the mental game of solving a crime. He takes pride in his mental abilities that enable him to solve a crime. Holmes also is unselfish when he tells Merryweather he wants no reward beyond his expenses for stopping the robbery.
Merryweather is respected as the director of the City and Suburban Bank. He's overconfident, worrying more about missing his card game than about his bank vaults.