Final answer:
Atticus calls Mrs. Dubose a great lady because she successfully overcomes her morphine addiction, demonstrating significant personal courage and strength of character.
Step-by-step explanation:
Atticus calls Mrs. Dubose a great lady because she beat her addiction. In Harper Lee's novel, To Kill a Mockingbird, Mrs. Henry Lafayette Dubose is seen as a cantankerous and bitter old woman.
However, Atticus Finch admires her for the courage and determination she shows in her fight against morphine addiction. In the context of the novel, her struggle is symbolic of the greater moral battles that individuals face and the strength of character required to confront personal demons.
It is this determined struggle to overcome her dependency, despite the difficulty and pain it caused her, that leads Atticus to refer to her as a 'great lady.'