Tom Hiddleston (the actor behind Loki in the Marvel Cinematic Universe) once said, “Every villain is a hero in his own mind.” Even some of the most rotten villains in fictional history have justifiable motives.
The Wicked Witch (at least initially) doesn't want revenge, she wants justice for her sister. When it's clear that her request for a fair trail is going to be denied, the Wicked Witch asks for her sister's shoes back and the (allegedly) Good Witch tells Dorothy, "Their magic must be very powerful or she wouldn't want them so badly." Or you know, maybe the Witch just has a problem with her sister's murderer wearing her clothes.
The Good Witch then threatens to drop a house on the Wicked Witch (sidenote: we need to re-think these names). Imagine reporting a crime to the police and cops respond by threatening to murder you if you bring it up again. That's how the criminal justice system works in Munchkinland.
When Cersei asks about her children, Maggy tells her, "Gold shall be their crowns and gold their shrouds... And when your tears have drowned you, the valonqar shall wrap his hands about your pale white throat and choke the life from you." This interaction informs Cersei's character throughout the whole series. Everything she does is based on the belief that a "valonqar" (or "younger brother") will kill her and her children. With that in mind, it's easy to understand why she doesn't trust Tyrion. In fact, her treatment of Tyrion is actually pretty kind considering the fact that she believes he will kill her children.
Let's also consider what this sort of prophecy would do to a child. Cersei knows that her whole life is set in stone. She's married to an abusive alcoholic and she knows she is powerless to change it. She knows one day her children will be taken from her. This knowledge would drive anyone to madness and in this light her paranoia is much more understandable.
Triple 9 is a heist film starring Casey Affleck, Chiwetel Ejiofor, Anthony Mackie, Aaron Paul, Norman Reedus, Woody Harrelson, and Kate Winslet. Basically it has more stars than Tatooine. Let's get this out of the way, Kate Winslet's character, Irina Vlaslov, is not a good person. She's a murderer and a racist and the first time we see her, she throws a bag of teeth at a kidnapped couple (who's teeth? no idea). But she's not the villain of the film. Circumstance is. Like almost every other character, Vlaslov reacts to her environment. She exists in a moral gray area (well, probably closer to the dark side) and everything she does is to save and protect her family: her husband, her sister, and her nephew.
Like the Wicked Witch of the West, Maleficent had a whole film to prove her innocence, but even in the original movie, she wasn't a horrible person. When she arrives at the party (uninvited, but that's more of a faux pas than a crime), she's told that she is not wanted. What a heartbreaking thing to hear. Maleficent just wanted to be invited to the party, something that the middle schooler inside of all of us can relate to. And even though she wasn't invited, she still gives Aurora a gift. Sure it was a curse, but at least she put some thought into it. It's not like she gave her a gift card or anything.
In The Emperor's New Groove, Ertha Kitt plays the "evil" advisor Yzma and David Spade plays an Incan version of David Spade. After being fired by the cocky Emperor Kuzco, Yzma seeks revenge. She attempts to kill Kuzco with the a potion and claim the throne for herself. On a surface level, she seems bad. She covers a lot of the major "no-no's": murder, coveting stuff, brewing potions.
However, what most people don't realize is that Yzma wasn't just Kuzco's advisor, she was his foster mother, his adoptive parent. That's right Kuzco was a terrible ruler who basically fired his own mother because she was meddling in his affairs (i.e. trying to successfully run the country). Kuzco was an unfit ruler and by overthrowing him, Yzma was doing what was best for the realm.
Dolores Umbridge was not the hero Hogwarts deserved, but she was the one they needed. On Pottermore, J.K. Rowling wrote that "Her desire to control, to punish, and to inflict pain, all in the name of law and order, are, I think, every bit as reprehensible as Lord Voldemort’s unvarnished espousal of evil." However, the key phrase here is "in the name of law and order." Umbridge has a Machiavellian approach to leadership and she is at least justifiable in the way she runs Hogwarts.
From an outsider's perspective, Hogwarts had been terribly mismanaged. Teachers are freakishly loyal to Dumbledore and some seem radically under-qualified to teach magic (Trelawney). Dumbledore hired educators based on personal relationships rather than credentials. Under Dumbledore, several dark wizards found employment as Defense Against the Darks Arts teachers and one even played a role in the death of a student. This calls into question Hogwarts' whole background check system. And okay, yes, Umbridge was a speciesist, but she never had a problem with Professor Firenze, a centaur, because he was a competent educator. Umbridge put aside her personal beliefs because it was in the best interest of the students.
As Hogwart's Defense Against the Dark Arts teacher, she believed magical theory was just as, if not more, important than practical application. And she was absolutely right. Hogwarts' curriculum under Dumbledore was akin to giving a bunch of teenagers guns before teaching them how to use them. Hogwarts was an objectively dangerous environment and at least Umbridge tried to fix the problem.
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