Boo may be the ghost of Scout's neighborhood, but Mrs. Dubose is the dragon. Scout introduces her as "plain hell" (1.14):
Jem and I hated her. If she was on the porch when we passed, we would be raked by her wrathful gaze, subjected to ruthless interrogation regarding our behavior, and given a melancholy prediction on what we would amount to when we grew up, which was always nothing. (11.3)
Despite being confined to a wheelchair most of the time, Mrs. Dubose inspires rage and fear just through the power of her words. Closer up, her appearance alone is enough to gross Scout out:
Cords of saliva would collect on her lips; she would draw them in, then open her mouth again. Her mouth seemed to have a private existence of its own. It worked separate and apart from the rest of her, out and in, like a clam hole at low tide. Occasionally it would say, "Pt," like some viscous substance coming to a boil. (11.86)
For Scout, Mrs. Dubose is a distressing, barely human force that takes over their afternoons after Jem goes crazy on her camellias. It's not until after she dies that Scout and Jem get a sense of what's going on behind the drool and venom: Mrs. Dubose is a morphine addict who had vowed to go clean before she died, and enlisted Jem and Scout (without their knowledge) to keep her off the stuff for longer and longer periods of time. Atticus tells the kids the lesson he hopes they've learned from her.
"I wanted you to see what real courage is, instead of getting the idea that courage is a man with a gun in his hand. It's when you know you're licked before you begin but you begin anyway and you see it through no matter what. You rarely win, but sometimes you do. Mrs. Dubose won, all ninety-eight pounds of her. According to her views, she died beholden to nothing and nobody. She was the bravest person I ever knew." (11)
Even though no one would have blamed Mrs. Dubose if she had wanted to leave this world in narcotic bliss, she decided to try to do what she felt was right, no matter how impossible it seemed or how painful it was.
Hmm, sounds like a person whose name begins with "A" and ends with "tticus."