Tom Robinson showed compassion for Mayella Ewell in helping her with small jobs around the Ewell home. Ironically, it was his kindness that led to Tom's being falsely accused of rape, the situation that led to his death. When Tom was testifying at his trial, he made the mistake of saying that he felt sorry for Mayella; as a black man, he was not allowed to express human compassion for a white person, for it suggested that he felt some sense of superiority. This was one element of racism that permeated his trial.
Heck Tate showed compassion for Boo Radley in the novel's conclusion when he refused to acknowledge that Boo had killed Bob Ewell. Heck insisted Ewell fell on his knife so that Boo would be spared being placed in the public spotlight. Heck knew that being exposed to public scrutiny, even public approval, would be sheer torture for the reclusive Boo.
Also, at the end of the novel, Scout walks Boo home, holding his hand. She speaks to him very gently, allaying his fears. Scout has come to realize how emotionally fragile Boo is, and she treats him with respect and special kindness.