These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Robert E. Lee "Bob" Ewell personifies all that was wrong with the 1930s. He gets Tom Robinson, a disabled black man, arrested for supposedly raping and beating his daughter Mayella. Atticus, the defense lawyer, shows that Tom was physically incapable of committing the crime and that Bob caught Mayella making advances on an unwilling Tom and beat her himself. Since the book takes place in the Deep South several decades before the Civil Rights movement, the all-white jury sentences Tom to death anyway. Bob Ewell still also tries to take revenge on those that ridiculed him during the trial, including Tom Robinson's widow, a poor woman with many children to feed and a job that doesn't pay well. He yells obscenities at her as she walks past his house on the way to work. When her boss finds out and threatens to have him arrested for it, Ewell then begins to stalk her as she goes to work. When her boss again confronts him, Ewell claims that he couldn't be arrested because he never actually touched her. It's also implied at one point that Bob himself has been sexually abusing Mayella. Even though Tom Robinson is dead, Bob stays angry with Atticus for digging up the truth. As revenge, he tries to kill Atticus's children on their way home from a school play.
Iron Woobie: With the stuff he has to put up with, one could forgive Atticus for just giving up and leaving town. But he never lets all the bad things that happen break him. Even Tom Robinson's conviction, which almost totally shatters his belief in the justice system, doesn't break the man.
Jerkass Woobie: Mayella. While she's a very unpleasant young woman who has falsely accused an innocent man of assault, it's difficult not to pity her. She lost her mother at a young age, lives in poverty and squalor, struggles to raise her siblings with no help, has no friends, endures physical abuse from her father, and it's strongly implied that she endures sexual abuse from her father as well. She came on to Tom because she was lonely and he was the only person who had shown her kindness, and then was forced to falsely accuse Tom out of fear of her father.
One-Scene Wonder: Boo Radley, as played by Robert Duvall, in his first film appearance ever. He is onscreen for just a moment, and doesn't utter a single word the entire time, but manages to say everything he needed to only using his eyes.
Some Anvils Need to Be Dropped: Treating people unfairly because they have a different skin color from you is wrong. A similar moral in empathy is dropped with Boo Radley, who is shunned for being different. Remember, the novel was written in the 50's, briefly before, three white men savagely tortured to death Emmett Till, a 14-year-old black boy, for the "crime" of allegedly flirting at a white woman. The all-white jury acquitted the two killers despite being presented with irrefutable evidence of their guilt after only 30-minutes of deliberation (in fact, those two proceeded to boast of their crime in local newspapers, once safe in the protection of Double Jeopardy Laws).
Also Consider The Source. Anyone thinking rationally would take a second look at the accusation of Tom Robinson.
It's hypocritical to defend one group from persecution and then persecute another, as shown when Scout is utterly confused when her teacher talks about how horrible Hitler is for his mistreatment of the Jews, but had cheered on Tom Robinson's death sentence and then insulted the African American community at large.
Further underlined when during her lecture on Hitler's persecution of the Jews, a student expresses confusion that he would do such a thing because "They're white, aren't they?" Also, she begins the lesson by pointing out the importance of "Equal rights for all, special rights for none."
Scout's Aunt's church group sneering at the African-Americans while bemoaning how the native Africans live in "sin and squalor" and need to be evangelized.
The book's whole demonstration of the sheer cruelty of the racist attitudes in the Deep South.
She was often accused of not writing this one (especially since her "childhood friend" was a bestselling author in his own right). People who actually knew Truman Capote dismiss this tinfoil hatting by pointing out he would never have not taken credit for it.
Values Dissonance: Examined. The teacher Miss Caroline is quite displeased that Scout learned reading at a young age because it goes against the school system.
The Woobie: Tom Robinson. He's a nice quiet family man who minded his own business, and occasionally helped Mayella. Nonetheless, Bob Ewell decides to get him killed.
Also, Tom's wife. She does her best to make ends meet for her children after her husband is framed and killed, only to be endlessly harassed by Bob Ewell and considered to be living in "sin and squalor" by the local white women.