The most prominent character traits of Atticus Finch are his courage, his moral fortitude, and his dedication to a sense of justice. Through the novel, each of these traits is borne out by Atticus' actions.
Atticus's own actions in arguing the Robinson case demonstrate this kind of courage, and his behavior throughout embodies values of dignity, integrity, determination, and tolerance.
When writing about Atticus Finch, you may choose to write on all of these traits or choose one as a focus.
Courage and dedication to a sense of justice naturally fit together. The circumstances surrounding Tom Robinson's trial offer a number instances where Atticus shows courage in defending Tom Robinson, driven by his dedication justice.
The night before the trial, Atticus risks his safety to protect Robinson from a mob. Throughout the lead-up to the trial and its aftermath, Atticus risks his social position to adhere to his moral code, which is anchored by his sense of fairness and justice.
Additional evidence for Atticus' sense of justice can be found in the episode where he shoots a rabid dog. Here we learn that Atticus has given up shooting despite his prowess with a gun.
The neighbors tell them that Atticus is the best shot in the county, he just chooses not to shoot a gun unless he must.
Miss Maudie says that Atticus stopped shooting because he felt his gift with a gun gave him an unfair advantage. It would be unjust for him to use this gift because it would be unfair.