In Chapter 17, what opinion of Bob Ewell does Scout form based on evidence? And in Chapter 18, Judge Taylor felt who was browbeating whom?

Scout is already familiar with the Ewell family, but after Atticus questions him, Scout determines that Bob may have beaten Mayella himself. First, she believes that Bob fails to understand Judge Taylor's instructions when he warns Bob about "obscene speculations." But Scout discovers Bob's "evil intent" when he claims to have seen Tom "ruttin on my Mayella."

    Mr. Ewell reminded me of a deaf-mute. I was sure he had never heard the words Judge Taylor directed at him--

After Ewell spoke disrespectfully to Atticus, the defense attorney slowly made his case. According to Scout, Atticus reduced "the little man" back into being "a red little rooster." When Atticus determined that Ewell could write, and with his left hand, Scout understood that her father's line of questioning was meant to show that Bob could have hit Mayella with his left hand, while Tom could not.

Like Mr. Heck Tate, I imagined a person facing me, went through a swift mental pantominme, and concluded that he might have held her with his right hand and pounded her with his left. I looked at him. His back was to us, but I could see his broad shoulders and bull-thick neck. He could easily have done it. I thought Jem was counting his chickens.

In Chapter 18, Judge Taylor responds to Mayella's accusation that Atticus was "mockin' me." He explained that Atticus "is always courteous to everybody," and understood that if anybody was "browbeating," it was the angry Mayella.