Who Atticus is at the core is often best stated by Miss Maudie, a neighbor who I am sure saw him deal with the struggle of his wife's death and who has heard the trouble the town has given him on more than one occasion.
In chapter 5, during a discussion with Scout, Maudie says some pretty piercing things about Atticus. She calls him a Christian man, but not like the religious zealot Mr. Radey was. She notes that Atticus exudes humility:
“What I meant was, if Atticus Finch drank until he was drunk he wouldn’t be as hard as some men are at their best. There are just some kind of men who—who’re so busy worrying about the next world they’ve never learned to live in this one, and you can look down the street and see the results.”
What Maudie says here is that Atticus takes his Christian duty to be a man seriously and he lives it, he doesn't just talk about it.
On page 240, Alexandra and Maudie have a discussion that similarly shows Atticus to be a great moral man. He stands as the example for the town in matters of legal and moral ramifications:
“I can’t say I approve of everything he does, Maudie, but he’s my brother, and I just want to know when this will ever end.” Her voice rose: “It tears him to pieces. He doesn’t show it much, but it tears him to pieces. I’ve seen him when—what else do they want from him, Maudie, what else?”
“What does who want, Alexandra?” Miss Maudie asked.
“I mean this town. They’re perfectly willing to let him do what they’re too afraid to do themselves—it might lose ‘em a nickel. They’re perfectly willing to let him wreck his health doing what they’re afraid to do, they’re—”
“Be quiet, they’ll hear you,” said Miss Maudie. “Have you ever thought of it thisway, Alexandra? Whether Maycomb knows it or not, we’re paying the highest tribute we can pay a man. We trust him to do right. It’s that simple.”
This set of dialogue indirectly shows Atticus' position in the town. I recommend either of the bolded quotes, but left you the discussion to look at in case you have a particular direction you were already going.