There are two main characters who are isolated due to stereotypes: Boo Radley and Mayell Ewell. Both of these characters are victimized by their reputations in Maycomb’s critical society.
Boo Radley has been isolated since he was a teenager, and most of the people in Maycomb think he is a freak or a monster, and at best a sad curiosity. His reputation is built on distant events and legend. The son of strict religious parents, he never leaves the house, except on rare occasions when he can help the Finch children.
Mayella is isolated by poverty. Everyone in Maycomb assumes once a Ewell, always a Ewell. All Ewells are uneducated and content to stay that way. Mayella grows flowers, and falls in love with Tom Robinson. She is clearly not what everyone thinks she is. Yet Mayella is completely isolated, and lives in squalor because she was born a Ewell.