Ms. Hoover is an alcoholic who shows very clear signs of depression which is not ideal given that she's responsible for a classroom full of second graders. Clearly, it's taken a toll on her teaching abilities..
Key Line: "Since we have fifteen minutes until recess, please put down your pencils and stare at the front of the room."
As the school bully, Nelson is frequently painted as a villain, but when you actually stop to think about the fact that he's a ten year old boy whose dad walked out on him, and who has obvious issues at home, his anger issues suddenly start to make a lot more sense.
Key Line: "I'm going away for a week. Cya!" (His mother does not seem to care if he disappears for long stretches of time.)
The words "Ned Flanders" and "Dark" don't seem like they mix, but beneath his sunny exterior lies a whole mess of disturbing shit. In the episode "Hurricane Neddy" we learn that Ned was once a troubled child whose beatnik parents essentially subjected him to a year long beating that forced him to suppress all of his negative impulses, and instead replace them with all those "Diddleys" and "Doodleys" everyone knows him for. Though he vows at the end of the episode to express his rage like a healthy person, it's pretty clear that he reverts back to being one big ticking time bomb of repression.
Key Line: "...And if you really tick me off, I'm gonna run you down with my car."
Laurleen's tenure on The Simpsons was brief but soul crushing. She begins her arc as a struggling cocktail waitress who tries to seduce Homer (with a downright beautiful song) because he's the only man that's ever treated her with an ounce of respect. Homer eventually rejects her advances, and she apparently takes it pretty hard because the next time we see her, she's clearly drunk and her voice actress has switched from Beverly D'Angelo, to the woman who does Lunchlady Dorris. (Note: Apparently she comes back in Season 19 but i'm not gonna talk about that because, well, fuck that...)
Key Line: "I spent last night in a ditch."
Mrs. Skinner is painted as the quintessential overbearing mother, but I would argue that the opposite is true. There's a lot wrong with the episode "The Principal and the Pauper", in which it turns out Principal Skinner is actually an impostor named Armin Tanzarian, but I would argue that the worst part of it is the old woman's willingness cut her biological son out of her life forever (by tying him to a train no less) in favor of the man that stole his identity.
Key Line: "I'm sorry, Seymour. It's nice you're alive, but you're just not what I'mlooking for in a son. I'm glad you understand."