Mr. Ewell had a negative character which was clearly visible in Mayella's responses and body language in the courtroom.
Explanation:
Mayella's father, Bob Ewell is not a good person, he is a drunkard who beats his kids when he's drunk, he is also a racist. When Atticus asked Mayella about her father, her responses were unnatural. It also seemed like she was scared of him whenever she looked at him across the courtroom while answering the questions about him.
Her body language showed that she was not comfortable while answering the questions about her father. From her responses, we can imply that Bob Ewell was the type of person who didn't treat his daughter very well, he had a dominating nature upon his family and everyone in his family is scared of him including Mayella.