The aesopian fable of The Frogs And The Sun is generally considered a cautionary tale against tyranny, the frogs begging the gods to not let the Sun marry or else another Sun will appear and kill them by drying away their marshlands. Hell, one version even has Helios ask the gods for counsel in marriage, and they waste no time telling him to not even think about it.
Discussed by Ishmael in Moby-Dick, in relation to the creepiness of albinism in spite of the good symbolism of white.
In Harry Potter: Dolores Umbridge. Besides her obsessing with Tastes Like Diabetes imagery, she, unlike the main villains, can summon a Patronus like the protagonists. Even better, she can do so while wearing an evil Soul Jar on her neck while everyone else can't. In other words, an animal shaped avatar of light powered by her utter sadism. Yeah.
You could also count that Voldemort became an albino, not to mention that the Malfoys, who also served as antagonists, are blonde.
Crenshinibon, The Crystal Shard from the Drizzt Do'Urden-centric Forgotten Realms stories, is a psychotically evil artifact with the power to do almost anything—as long as it bathes in the light of the sun every once in a while. The liches who made it were unusually Genre Savvy, and made the thing work on those principles because they liked the irony. Then, just to prove its own Badass credentials, Crenshinibon ate them.
In The Riftwar Cycle by Raymond E. Feist, the Valheru Ashen-Shugar dressed in golden armour with a white tabard and rode a golden dragon. And while he may have had some faint feeling of responsibility for the land and the people enslaved under his rule, he was still Valheru all the way.
In Neverwhere, the Big Bad turns out to be soft-spoken, kind and caring angel Islington. Well, not that kind and caring, actually. They don't kick you out of Heaven for nothing.
Very much present in the Alex Verus series. The "Light Council" aren't necessarily bad guys, but there's a reason Alex doesn't trust them. The author even lampshades the trope in one of the world-building articles here.
The villain (well, he starts out good and gets steadily more villainous as the series goes on) of Janny Wurts Wars of Light and Shadow is a handsome, blond, blue-eyed guy who wears white and gold and wields the elemental power of Light. He sets himself up as a deity and has the hero, who has black hair, green eyes and the elemental power of Shadow, hunted down as the embodiment of all evil.
In Albert Camus' noir novel The Stranger, strong sunlight generally accompanies unpleasant moments in the narrator's life. The day of his mother's funeral and his murder of the Arab that eventually sees him sentenced to death both take place on bright, brutally hot days.
In Robert Jordan's The Wheel of Time, the Children of the Light believe themselves to uphold the 'will of the Light' when, in fact, they generally do more harm than good. Particularly the Questioners.
There's also one of the series main villains, Lanfear, who always wears white and silver and surrounds herself with light, but is the second-most powerful of the Forsaken (only Ishamael beats her) and generally one of the most infamously evil people in history. Ironically, her name means "Daughter of the Night", so she legitmately uses light and dark symbolism.
A borderline case that nonetheless is a good illustration: A recurring theme in Susan Cooper's The Dark Is Rising series is that, although the Light is Good, in the sense that everything it does is to protect humankind, it's not nice. This comes up most explicitly in The Grey King, in a conversation between Will Stanton (a representative of the Light) and John Rowlands (an ordinary human): "At the center of the Light there is a cold white flame, just as at the center of the Dark there is a black pit bottomless as the universe."
That conversation also causes Will Stanton to suspect that the Light is what originally caused him to become so severely ill he was sent to Wales to recuperate... making him conveniently available to do the Light's work.
Lord Rahl, the villain in the first Sword of Truth novel is a Villain with Good Publicity who dresses in white robes, talks a lot about peace and harmony, and generally does a pretty good job at convincing everyone that he's The Messiah. The impression is somewhat ruined by the fact that Lord Rahl's first name is "Darken"...
The sisters of the light, while well intentioned, are often seen as a hindrance throughout the first half of the series, especially when many of them are captured and enslaved by the Big Bad and used for evil.
Evangeline Walton's Prince of Annwn (a very loose adaptation of Welsh legend) features as its primary antagonist Havgan, a god of light and beauty — but also sterility and disease. He is heavily implied to be an Expy of real-world Babylonian mythology's Nergal, who had a similar portfolio; his heroic opponent, by contrast, works for Arawn, Lord of the Dead and poster boy for Dark Is Not Evil.
The gods of Order in Louise Cooper's Time Master Trilogy are hardcore Knight Templar fundamentalists with an insane lust for power and worship. Tarod and the gods of Chaos range from slightly Chaotic Evil tricksters to fairly Chaotic Good, going through almost every shade of Chaotic Neutral, but they're always portrayed in a much more positive light than the always psychotic gold-and-white-clad gods of Order.
Discworld novel Thud! does this a fair bit when describing the philosophical beliefs of the Dwarfs. As a subterranean race, light and darkness have very different connotations for them, so that "becoming enlightened" is not a good thing.
However, in novel, the dwarves that believe that becoming enlightened is bad repeatedly cross the Moral Event Horizon, and are evil. The 'enlightened' dwarves are modern and progressive, and the heroes of the novel.
This is not exactly the case. The fundamentalist dwarfs have reduced the tenants of their de facto religion into simply sitting in the dark and pretending that light does not exist. Others, like Grag Bashfulsson, consider darkness a state of mind, not a lifetime spent sitting in a cave. He and those like him are still 'endarkened', which to dwarfs is the same as 'enlightened' to humans.
Lady Lilith A.K.A.Lilly Weatherwax is every inch the good fairy god mother, save for the moral compass.
In Wintersmith, after Tiffany Aching dealt with the crush the Wintersmith had on her that threatened to turn at least the continent dark and cold forever by properly releasing the summer, she is shown what the opposite would have been—the deep, deep desert, so bright and hot that nothing can survive.
Also, elves, largely thanks to their Glamour. One of the names used to refer to them is "The Shining Ones".
Good Omens, by Terry Pratchett and Neil Gaiman, plays with this theme; Aziraphale and Crowley often squabble over who does what, heavily implying that good and evil are all perspective. The forces of light are also destructive and more than happy to bring about the Apocalypse, especially the Metatron.
Another example would be Pollution, one of the Four Horsemen of the Apocalypse (having taken over from Pestilence), who is described as being pale and white-haired.
Unusual case that comes paired with Light is Good. Aslan is always associated with light, but his is fertile and gentle whereas Jadis' and the Lady's are sterile and poisonous.
Dorian Gray of The Picture of Dorian Gray is blond and angelic looking in very sharp contrast to his actions. Problematically, a number of book covers as well as the derided The League of Extraordinary Gentlemen film present him as Tall, Dark and Snarky. Gray actually starts out as a very angelic and pure person, only to be slowly corrupted as the book goes on. And while he does remain blond and angelic, his painting makes it pretty clear that his inside looks quite different. When he stabs the painting at the end, his body does change to look as horrible as his personality and actions have been.
In Waywalkers and Timekeepers, the Light is the most powerful weapon in existence, and the only one able to defeat the Big Bad Cronus. To use it, the protagonistSatan has to tap into the fear of every human on earth, and may lose his own mind in the process.
Although it's implied that when he was still actually 'The White' he wasn't evil yet (though starting to lean in that direction). When he takes the actual step to become evil (while maintaining that he's doing it 'for the greater good'), he breaks the White and becomes Saruman of Many Colours. Even that continues the symbolism, echoing the way white light splits into a rainbow when shone through a prism.
From the same author, Roverandom has The Great White Dragon, although admittedly he's not as impressive a villain as Tolkien's famous dark lords.
Tolkien was well aware of that darkness and light can be used as metaphors of evil and good, but also the reverse, more rarely. For ex, there are moments when Frodo and Sam find themselves thankful for the omnipresent cloud and shadow of Mordor, since it helps to hide them from the Eye of Sauron and lesser evils. Minas Morgul radiates a sick, corrupted light that is so terrifying and maddening that simple familiar shadow and darkness become a welcome source of shelter and protection when they hide you from it. In that case, darkness was good and light evil.
Also, in some accounts of the Silmarillion, Melkor the Morgorth originally manifested himself physically as a brilliant, beautiful light...Tolkien himself was well aware the 'Lucifer' means 'light bringer' or 'light bearer'.
In the context of Tolkien's mythos, the Sun is not good for the elves, who see it as symbolic of the triumph of men over them (it is outright stated that the Sun symbolises the waning of the elves, and Galadriel implies in The Lord of the Rings that they see the dawn in the same way mankind sees the dusk - as symbolic of the end).
Mrs Coulter, who is a beautiful, charismatic person and yet probably the most fucked up villain to ever show in the series. The movie made her a blonde, only to stress this trope. Also, her monkey daemon is golden in colour.
The tualapi, which are white birds that cause destruction on the mulefa's world.
R'hllor is the Lord of Light and a god of fire, who supposedly stands in contrast and eternal conflict with the Great Other, the icy and evil god of darkness. However, judging from the actions of his clergy, such as Melisandre, the religion comes across as far from pure and good. Melisandre in particular uses blood magic and human sacrifice to perform miracles, and is an altogether ruthless Knight Templar. When called to task, however, she does give persuasive justifications for her actions, which she sincerely believes will save lives. The fact that R'hllor's apparent enemies are Obviously Evil also helps justify her cause, but it might be a question of Black And Black Morality. The darkness and cold versus fire and light conflict, as well as the name of the series, call up Robert Frost's poem "Fire and Ice," in which both extremes are equally destructive.
The Kingsguard are supposed to be paragons of chivalry. They wear pure white cloaks and shields to show that they have renounced all familial ties, but the additional connotations of purity and goodness are obvious. Unfortunately, they are tasked with serving the king unquestionably, which sometimes makes them brutal enforcers of a mad despot.
After Cersei grants Qyburn a lordship, he starts wearing an outfit that's a combination of a maester's garb and a Kingsguard outfit (so monastic robes but in elegant white and gold). Qyburn is a depraved Mad Doctor and Torture Technician that is Mengele in medieval clothing.
In Laurell K Hamilton's Merry Gentry series most humans automatically assume the "Light Court" of the Seelie is good and the "Dark Court" of the Unseelie is evil. In truth things are much more complicated.
In particular the King of the Seelie Court, Taranis, "Lord of Light and Illusion" who is a batshit insane rapist willing to let his people die rather than give up power.
The White Court vampires in The Dresden Files. No they won't drink your blood, just all your emotions, will and finally life force, but by then you won't care.
Also the Wizards White Council is theoretically the good guys but is so riddled with political backstabbing and dealmaking and so rigidly bound by it's traditions that in practice it falls more somewhere between True Neutral and Lawful Neutral. At best.
The Summer fae also have elements of this. Yes, they're The Fair Folk, but they're somewhat benevolent and generally on the side of life. Except Aurora, the former Summer Lady, was so pissed off at the state of suffering engendered by Summer and Winter that she wanted to bring about the end of the world so it would all stop, and Titania, the Summer Queen, keeps finding ways to fuck with Harry for killing her, even though he saved the world in the process.
That and while the Winter Court represents the bad things of darkness, freezing cold, and death, the Summer Court represents the equally bad things, like scorching heat, infestations/plagues from too many harmful living things, and unending, uncontrolled life. (like, you know, cancer.)
The Archangel Uriel ("Light of God"), while presented as a good guy, is distinctly not a nice guy. In fact, he is more accurately described as heaven's "spook": the assassin of Heaven who took the first born of Egypt, among other shady aspects of the business of safeguarding humanity and free will.
Played for all it's worth in Ghost Story. When Harry calls Uriel "Uri", the the Archangel nearly annihilates him. "Uri" or in english "my light" can mean something very different than "Uriel" The Lord is my light. Still scared out of his spirit mind, Harry decides to call him "Mr. Sunshine". Uriel bemusedly accepts it.
The Forces of the Light from Grunts!! are perfectly willing to kill female and young members of the Dark races for no apparent reason other than that that is what Light warriors do and are monumental jerks about it. Then again, seeing as the dark races tend to kill and eat members of Light and Dark races for no reason...
Something of a point is made of this in Zilpha Keatley Snyder's Green-Sky Trilogy. The tree-dwelling Kindar are ruled by a priestly class who are the only ones allowed to wear pure white clothing. The priests — and the reason for their existence — are what's killing off the psychic powers and the three principles the culture needs to survive. In the third book, they all get kicked out of their palaces, but a few hang onto their principles and their white outfits until both are filthy, tattered rags.
Katherine Neville's The Eight, a historical fantasy novel about alchemy, espionage and chess, has the "good guys" representing the black pieces on the chess board, and the evil guys representing the white pieces.
Diana Henstell's NEW MORNING DRAGON. When the Devil comes to New Morning, he always dresses in bright white suits.
In the Dune mythology, a woman in mourning wears yellow. Because the desert is death during the day, or something.
1984: "The place where there is no darkness" is not a place you ever want to end up. Ever.
While the forces of Light are more often the heroes than the villains in Night Watch and its sequels, their Utopia Justifies the Means mindset occasionally makes them as bad or worse than the selfish, but not unnecessarily sadistic, forces of Darkness. The Nazis, among other horrors, were among their failed attempts to change the world.
Believe it or not, the Cthulhu Mythos invoked this trope occasionally. One of Yog-Sothoth's avatars is Aforgomon, a being worshipped as the god of time who only manifests himself to those who anger him, accompanied by blinding light. Among Nyarlathotep's forms there is the White Man, an angelic looking blond man with white robes, and the Black Pharaoh, who despite the name dresses himself in brightly coloured clothes.
The titular abomination in The King in Yellow is often depicted as an angel with yellow robes.
The false Lightbringer in the Reign of Istar Dragonlance trilogy. Though he started out the ultimate good, and grew to be consumed by a bright light aura, he quickly turned on the followers of the Neutral Gods after he'd removed the followers of the Dark Gods from his kingdom (or continent). After they were out of the picture, he soon turned on the followers of the Gods of Light that were not devout followers of his specific god.
Dragonlance in general develops a really weird version of this towards the end, where it's revealed that the Good isn't Good. Neutral is implied to be the ultimate Good while Good and Evil are equally evil. Somehow. It resulted in a minor case of Broken Base.
In The Heart of the World series the predominant color of the Darwinist religion of Mann is white.
The House of Night series by P.C.Cast and Kirsten Cast. One of the books actually has the line "Remember, darkness doesn't always equal evil just as light doesn't always equal good." And later in the book Burned there are two bulls and the white one is evil and the black one is good. meaning it's bad when Stevie Ray accidentally summons the white bull thinking it's the good one.
In the first book of the Coldfire Trilogy, Senzei is tricked into consuming the Fire (water laced with solar fae) by a demon masquerading as Ciani who tells him that it will turn him into an adept. It doesn't end well for him at all.
"Daylight can't hurt you" she had said, but Senzei realized it could, in enough quantities. It could dehydrate, burn, inspire killing cancers...
Sol from Warrior Cats. His name means Sun, but make no mistake, he was the Big Bad for a while.
Many (though not all) Free Magic creatures (which are the equivalent to Eldritch Abominations or demons, depending on type and magnitude) in the Old Kingdom books are extremely hostile to life as we know it, and are often white in color and/or surrounded by a kind of fierce white light (Mogget's unbound form being a prime example). The other main type of antagonistic beings, the Dead, are generally presented as creatures of smoke and shadow, so Dark Is Evil is in effect as well.
Although not strictly a villain, the Seventh Doctor in the Doctor Who New Adventures was a lot more of an Anti-Hero than he had been previously in the series, being a ruthlessly manipulative Chessmaster fond of using his Omniscient Morality License to justify committing all sorts of morally sketchy acts. To juxtapose against this, the writers changed his costume from the shabby clothing he'd worn on TV to a smart cream / off-white suit.