What opinion do the other characters have of Bill in the "Ransom of Red Chief?"

Because of the detached first person narration of O. Henry's story "The Ransom of Red Chief," determining any opinions that characters have for each other is more a matter of assumption than certainty. The characters who Bill interacts with to any significant degree are the boy, "Red Chief"; Sam, the narrator; and Ebenezer Dorset, the boy's father.  

Sam seems to view Bill as slightly less intelligent and talented than himself. Sam comes up with...

Because of the detached first person narration of O. Henry's story "The Ransom of Red Chief," determining any opinions that characters have for each other is more a matter of assumption than certainty. The characters who Bill interacts with to any significant degree are the boy, "Red Chief"; Sam, the narrator; and Ebenezer Dorset, the boy's father.  

Sam seems to view Bill as slightly less intelligent and talented than himself. Sam comes up with the ideas and assigns Bill his role, fully expecting Bill to comply. Sam seems to believe Bill is too squeamish about handling the boy, for he states that Red Chief "terrorized [Bill] from the start." The narrator's description of the way Bill cries out in fear when nearly being scalped suggests that he thought Bill was not as brave in the face of danger as he could have been:          

They were simply indecent, terrifying, humili­ating screams, such as women emit when they see ghosts or caterpillars. It’s an awful thing to hear a strong, desperate, fat man scream incontinently in a cave at daybreak.

At one point, Sam fears for Bill's sanity, and when he agrees to pay the ransom, he does so because Bill "had the most appealing look in his eyes I ever saw on the face of a dumb or a talking brute."

Similarly, Red Chief must sense that Bill is easily manipulated and not very intelligent, making him all the more brutal and persistent in the torments he subjects Bill to.

Finally, Mr. Dorset realizes that Bill is completely terrorized by the boy, so when Bill asks him how long he can hold off the child, the man bluffs that he can probably only contain him for ten minutes. Dorset is easily able to outwit the petty criminals because he recognizes the lack of intelligence and wisdom in both Sam and Bill. 

Again, the reader must consider the biased perspective of the story when it is told only from Sam's perspective. Sam makes himself look better by emphasizing Bill's fear, weakness, and lower intelligence. Part of the irony of the story is that Sam shares in those same faults to a great degree.