What are some examples of the coexistence of good and evil in To Kill A Mockingbird?

Although most characters in To Kill a
Mockingbird are clearly on the side of good (Atticus, Miss Maudie) or evil
(Bob Ewell), a few are conflicted in their
morality:

• Walter Cunningham,
  Sr.: once a member of a lynch mob that sought vigilante justice against
  Tom, Walter, Sr. became a more tolerant and empathetic man by the end of the
  novel.


• Mrs. Dubose: once the
  vitriolic berater of children, Mrs. Dubose showed great courage in battling her morphine
  addiction


• Aunt Alexandra:
  once a champion of Southern Aristocratic debutante values, Aunt Alexandra is more
  accepting and open-minded once the trial begins and she sees the effects of racism on
  her family

Even a few
institutions are places where good and evil
coexist:

• Scout's
  school: Miss Fisher tries to teach the class to read while--at the same
  time--telling Scout she learned to read all wrong.
  


• Maycomb County Courthouse:
  Atticus' closing statement urges equality for all.  Judge Taylor is an
  honorable man, but the antics of Mr. Gilmer, Mayella and Bob Ewell reveal that no real
  justice can befit Tom Robinson