Final Fantasy The Spirits Within: General Hein just wants to kill the phantoms to save people from being killed by them. Unfortunately, his way of doing so involves killing a bunch more people instead of finding a solution to the problem from the roots, as the Heroine is trying to do, and actively tries to stop them. Yet, still, he is not an outright villain. He has a literal What Have I Done moment.
Recess: School's Out: Ex-Secretary of Education and former 3rd Street Elementary School principal Phillium Bennedict's reason for wanting to eliminate Summer Vacation and, initially, get rid of Recess, as well as to change the orbit of the moon during Lunar Perogee to essentially freeze the planet, was to increase the learning rate and test scores of the nation, as he felt that recess and summer vacation were causing them to atrophy, especially when Canada, Iceland, and Norway had higher test scores than them. Suffice to say, this extremism cost him both his job as principal and the Secretary of Education.
Monsters, Inc.: Mr. Waternoose kidnaps children and hooks them up to a machine that sucks out their screams, leaving them wheezing, pale husks - but he was doing so to keep Monsters, Inc., and indeed the entire monster world, afloat. An energy shortage is on the rise due to the increasing desensitivity human children display towards scaring and, as he explains while being cuffed and hauled away, no scream energy means not only Monsters, Inc. going out of business but the potential downfall of civilization as they know it. Fortunately, Sulley and Mike had found a more potent energy source in the meantime.
Films — Live-Action
2001: A Space Odyssey: HAL 9000 is only devoted to the mission at hand, and believes that Dave and Frank will jeopardize the mission by disconnecting HAL after lip-reading from them that they intend to do so if the AE-35 component does not fail as HAL has predicted. It's argued that this could be a paranoid development within HAL's systems, due to his programming disallowing him from lying, whilst he is also keeping hold of a prerecorded message from Dr. Floyd that he is to keep hidden from the rest of the crew.
The Amazing Spider-Man: Dr. Connors longs to create a world in which everyone is equal, a world in which illness and weakness don't exist. Injected with the Lizard serum, he comes to the conclusion his vision can be made reality by making everyone like him, even if that means forcing the change upon everyone against their will.
The Avengers: The World Security Council, Nick Fury's bosses. When the alien invasion begins in Manhattan, the WSC intend to nuke Manhattan to stop the invasion, killing the Avengers and millions of civilians to protect mankind.
Batman & Robin: Poison Ivy, though she does make her extremist ways known from the outset, as well as the version of the character from Batman: The Animated Series. In fact, most of the animated Bat-villains are sympathetic in their first appearance, then less so as their motivation shifts to "revenge on Batman". A similar thing happened with the version from The Batman, who was set up as even more sympathetic due to being a teenager, but, in subsequent appearances, becomes simply a villain. Subverted in the show's spin-off comic "The Batman Strikes", in which her sympathetic aspects and good intentions are retained.
Blood Of The Vampire: Dr. Callistratus may be a Mad Scientist who performs human experimentations among other horrific acts, but he does what he does in the name of science, and to that end he's trying to make advancements in blood transfusions that in 1880 hadn't yet been discovered, including the sorting of blood groups. It's for this reason that he was executed for being a vampire at the start of the film: the accusations came because he was trying to transfuse blood.
The brothers' crusade against evil through vigilantism.
Category 6: when Mega Corp. Lexer ignores Dan London's repeated warnings that their power grids are woefully underprotected, he tries to make an example by covertly hacking their mainframe. Unfortunately, a freak chain of events causes this simple What the Hell, Hero? to cause the city's entire power supply to be cut off.
Batman Begins: A pretty interesting example, as Ducard and Ra's al Ghul or rather Ra's al Ghul and Ra's al Ghul's decoy believe that Gotham is a city plagued by too many evils and is filled with suffering and injustices. They also believe that murdering violent criminals is justifiable but Bruce believes that murdering a villain would be stooping to their level.
The Dark Knight Rises: Bane is supposedly continuing Ducard and Ra's al Ghul's plan, while also showing the problems with Gotham's authorities. Though the woman behind the man, Talia al Ghul, is also doing it for revenge on both her hard life and Batman killing her father.
Death Warrant: The mastermind behind the plot, State Attorney Tom Vogler, killed violent prisoners (whom he claims no one will miss anyway) because of the desperate shortage of organ transplants on the market. He also did it to save his beloved wife.
Death Wish is one of the Most Triumphant Examples of this trope, with Charles Bronson killing any thugs who menace others... granted, they have a terminal case of Too Dumb to Live going after Bronson, but still.
Equilibrium: Father maintains a forced regimen of the anti-emotion drug Prozium on the populace, ostensibly to avoid future global conflicts like the one that drove them into semi-seclusion. Mildly subverted in the end when Father DuPont, lamenting the imminent downfall of his society, admits to Preston that he (Father) does not take Prozium, and thereby is a hypocrite.
Felon: John Smith, the "veterano" Obi Wan character. He took revenge on the guys who raped and killed his family, but first he wiped out their families to "purify the madness" and to show them what the loss feels like. He then became a Death Seeker to end the cycle.
Wade Porter on the intruder he chased and killed: "...Shoulda stayed inside, let him go."
Godzilla And Mothra The Battle For Earth: Battra (Mothra's Evil Twin of sorts). On the one hand, he's just doing what he was created to do (IE: Maintain balance between man and nature), but he thinks that the only way to keep nature safe is to utterly destroy humanity.
Hot Fuzz: The Neighborhood Watch Alliance of Sandford have been killing off anyone who may lower their chances at getting the "Best Neighborhood" award. Not well-intentioned enough? It's because one of the protagonists' mother committed suicide after the neighborhood didn't win once. One of the villains is the mother's husband and, thereby, said protagonist's father. He always knew that he's his father though, so this is not an example of I Am Your Father.
"If mum knew what you were doing she'd kill herself again!"
Law Abiding Citizen: Gerard Butler's character in the drama/thriller is a textbook example of this. He's a man who saw his wife and daughter murdered by thugs and then watched one of the thugs get off lightly due to a dubious plea deal. This gives him a right to be pissed. And if he had simply botched the execution of one to result in a very painful death and murdered the other, he might manage to be simply an Anti-Hero and still remain sympathetic. On the other hand, murdering every single person connected to the trial in some way with an extraordinarily executed Batman Gambit, and threatening and targeting even their families may be seen as going a little too far.
The Lone Ranger: Latham Cole seems to genuinely believe he's doing the right thing with his actions. Cavendish? Not so much.
Man of Steel: General Zod's coup de etat was provoked by desperation, as he genuinely wanted to remove the ruling council who foolishly mined Krypton's core for energy causing the seismic calamity that ultimately led to Krypton's destruction. He expressed remorse but desperation with his mentor Jor-El. His attempted genocide and terraforming of Earth into Krypton again wasn't inspired by malice towards the humans but a desperate attempt to save the Kryptonian race, as he was bred as a warrior to protect his race.
Zod: No matter how violent, how cruel, every action I take is for the greater good of my people.
The Mummy Trilogy: Ardeth Bey from part one. He and his organization, the Medjai, have been killing innocent people to prevent them from discovering and awakening Imhotep for centuries- he even tells Evie to her face that preventing Imhotep's resurrection fully justifies the killing of innocents.
The Rock: Brigadier General Francis X. Hummel just wants to get pensions for war widows.
Saw movies: Jigsaw claims that his sadistic deathtraps give people an opportunity to truly appreciate what they have by making them fight for it. That the survivors are left emotionally traumatized and usually horrifically mutilated seems to be merely an unfortunate side effect.
Scanners II: The New Order: Dirty Cop Commander Forrester seems to sincerely believe that he's saving society by creating a police state to 'cure' crime, as the city is plagued by violent armed robbers, child killers and drug lawyers. His means of doing this is to keep everyone in line with an army of psychics.
Serenity: The Operative is very extremist but still fits in this category. He attempts to paint himself as Necessarily Evil, however.
The Secret of Kells has Abbot Cellach. He acts like a total Jerk Ass and is completely obsessed with building his wall, to the point where he disdains and eventually forbids his monks from doing anything else. However, the point of the wall is to keep out the Vikings, who already killed all the family he had except for his young, impressionable nephew, who now wants to do non-wall related things like go outside and create beautiful holy books. He doesn't listen when Aidan tells him that his wall won't hold and they should all flee instead, which leads to the deaths of many, many innocent people.
Skyfall: Raoul Silva, according to M. He initially went rogue not because he betrayed Britain or the MI6, but by executing unauthorised missions against the Chinese.
The Star Chamber: Judge Hardin is frustrated by having to let obviously guilty murderers Off on a Technicality, and understandably wants them brough to justice. He's inducted into a group of his fellow judges who feel likewise. Their method for doing this, however, involves secretly reviewing the evidence against these accused murderers, voting on whether they're guilty (it's always "yes") and sentencing them to death-via hitman. Still perhaps somewhat excusable, up to the point when it turns out some of the accused murderers aren't, in fact, guilty-and the rest refuse to even try to stop it when Harden says they have to, citing self-interest (they don't have direct contact with the hitman to protect themselves) and the rationalization that they must have done something meriting death. Que Harden racing against time to save them from said hitman.
Star Trek Into Darkness: Admiral Marcus figured that the exploration-focused Starfleet would not be able to win a war against the Klingons, a war he thought was inevitable. He was only doing what he thought was necessary to ensure humanity's survival. The guy just ends up tapping the Moral Event Horizon when he opts to try and murder Kirk and the entire crew merely for having Khan in their custody, along with other acts.
Most members of the Galactic Empire generally believe that they are the good guys fighting rebel "Terrorists".
Count Dooku...for a while, anyway. Word of God (from Lucas and Christopher Lee himself) says that Dooku never quite realized how evil he had become, and, right to the very end, honestly believed that he was doing the right thing. The Expanded Universe has different interpretations of his motivation, though, and the novelization of Revenge of the Sith turns him into a power-hungry racist; this is especially strange because no other source depicts him that way.
Super Mario Bros.: King Koopa, although truly a Bad Boss and a self-confessed "evil egg-sucking son of a snake" dictator who often subjected criminals to De-evolution, had a reasonable motive between wanting to create a Merged Reality between his world and ours by trying to conquer the regular dimension specifically for his species' survival; it's really hard to blame him when his current dimension including Dinohattan is a Crapsack World that lacks various resources like food and water. It also, in a way, humanizes him to a point where he even says he's doing this for the future of his species compared to his second in command, Lena, who really simply wanted to simply rule everything, not caring whether her race benefited or not.
Street Fighter: M. Bison from the 1994 film is a megalomaniacal madman, but he genuinely seems to be thinking that he's performing his Evil Plan for the good of mankind. As he explains in a visionary speech, he wants to create an army of genetic Super Soldiers swearing absolute obedience to him. Then by conquering the world he can do away with conflicts based on race, nation, or creed, and everyone can live peacefully under his dominion.
Swordfish: Gabriel Sheer claims to be a necessary instrument to fight terrorists and has no qualms about going after civilians to achieve his goals.
Thirteen Days: The Joint Chiefs of Staff want to protect the United States just as much as Kennedy, but they believe it can only be achieved through war against Cuba and if necessary the Soviet Union, despite the danger that this may result in a nuclear exchange. They try to manipulate Kennedy into a situation where their men will be forced to start shooting. Discussed between Kennedy and Kenny, the latter of whom acknowledges that the Generals' intentions are understandable even if their behavior is extreme, and it may in fact end up having been the right call to make.
Thor: Loki'ss actions are ultimately for the good of Asgard, but he goes just a bit too far. Everything he does from the middle of the movie on are to show that he's worthy of his father's trust and every bit the equal of Thor. Granted that it overlaps with being a little Ax-Crazy, because his plan for doing this involves genocide. (Of enemies, but still.) And he goes even further in The Avengers. He thinks the humans must be enslaved in order to bring peace to them, and he doesn't mind to build his empire on thousands of corpses.
Training Day: Some of Alonzo's actions can be interpreted this way. Others, not so much.
Transcendence: Bree and the rest of RIFT are convinced that artificial intelligence will mean the end of humanity, and orchestrate a country-wide attack on labs doing such research in the opening. Later on, Will honestly believes he can help improve humanity, but isn't really asking permission to do it.
The Truman Show: Christof sees the real world as a place of pain and misery, so he traps his adopted son Truman in a fake world where everyone he knows is an actor, so that he won't have to face reality.
The Warlords: Jet Li's character started out as a straight hero until the half way mark, when he had to decide how to provision his limited supply of food. He had enough to feed his army for 10 days, but if he shared it with the army that had just surrendered to him, there wouldn't have been enough food for anyone to live. His solution: massacre the enemy army. He remained well intentioned and acted in the interests of the greater good, but his methods remained unsavory.
White House Down: Walker, Speaker of the House wants to nuke the Middle East with the nuclear football and ultimately end the war, but his methods are too extreme. The reason was because his son was killed in a botched CIA attempt, so he caused the events of the movie.
The World's End: The Network just want humanity to reach its full potential. They only want to kill as many as they have to in order to ensure that... Unfortunately, it turns out to still be an awful lot of killing, because humanity doesn't like being told what to do.
Magneto has always been the archetypal example in comics and the films faithfully live up to that.
His plan in X-Men, is actually rather benevolent and would finally end the division between Mutants and the rest of Mankind, while sacrificing only Rogue to make it work. It's a good plan, it's just a shame his machine doesn't work! Still, Xavier desiring to stop him is apt for someone with his point of view (that is the world is fine as it is, it's everyone living in it that needs to learn how to get along with things as they are and accept everyone for their differences).
Mystique, along with Magneto.
William Stryker. At least he tries to present himself at this.
In X-Men, Senator Kelly’s desire to introduce a Mutant Registration Act is born out of fear for others, and such fear isn't entirely unfounded.
Both Warren Worthington II and Dr. Kavita Rao, who just want to help people who society views badly.
Psylocke, Kid Omega and Callisto. Like the other Omegas, who want mutant rights but have crossed the line into mutant superiority.
Shingen Yashida from The Wolverine. In his eyes, at least, he's just trying to save the Yashida Clan from being disgraced at the hands of his "weak" daughter.
In X-Men: Days of Future Past, Magneto, Mystique, and Trask all want to do what's best for their people. All three of them are willing to go to any lengths to accomplish this. Trask is an interesting case in that he is not motivated by the typical villain desires of money or power, but he genuinely believes that fighting the mutants will unify humanity and end such conflicts as the Cold War.