There are a number of characters in the text that could be considered heroes, I would suggest Atticus as a particularly strong example:
From the very outset of the story, his willingness to defend Tom Robinson despite overwhelming public pressure and his understanding of the task as a likely impossible one, his characteristics suggest that he is a heroic figure.
He also demonstrates hidden strengths and talents that even Scout knew little about and quashes her doubts about his strengths. She worries that he isn't strong as he just works in an office, etc., then he shoots the rabid dog and shows he has physical and relevant skills.
Most importantly, he is also willing to stand up to his children and point out when they are wrong. When Scout ruins the fllowers of Mrs. Dubose, he forces Scout to go read to her in order to learn a real lesson.