Babylon 5 has Vorlons, who look like angels and seem to be helping the younger species fight off the evil Shadows. However, it turns out that the conflict is not between good and evil, but order and chaos. Neither extreme is beneficial for the younger species, who are exploited as pawns in a deadly game. Ultimately, the younger species band together to kick both the Shadows and the Vorlons out of the galaxy.
In Battlestar Galactica (2003), the visions involving the Final Five are decidedly ominous even though the Five are clad in white robes and surrounded by white light. In addition, D'Anna is instantly struck down after trying to approach one of them. Yet the actual Five straddle more along the lines of Good Is Not Nice.
The Blackadder II episode "Beer" introduces Edmund's relatives the Whiteadders, whose piety and holiness stands in stark contrast to arch-cynic Edmund. However, it turns out that they're even more evil. Or at least she is; he's under a vow of silence and goes along with whatever she says, presumably for fear that she'll turn on him and burn him as a heretic. Until they both get rat-arsed on the eponymous drink.
There was a series called Brimstone. It had the same idea as Reaper, in which someone is forced to hunt Hell's souls because the Devil owns his soul, with Lucifer being a absolute Magnificent Bastardwho manipulates several parties against each other for his own Mephistolicious entertainment. Point was towards the end of the first season, his royal hoofedness shows up in front of the hunter of sinners, and gives a speech about how even the most damned souls can be redeemed. He then looks in the mirror and realizes he looks like Satan, and says to the hero that the first Angel someone sees is the way they perceive every Angel from that point on. Seeing as the show only had one season we never found out if this was Lucifer mucking with the guy or not.
One character (The Mole) pointed out that she had been a loyal worshipper of Baal, but had been condemned to hell because Christianity had "won" (in the Series, at least).
Season 4 gives us The Initiative. They're a government agency with sleek, white labs that captures and experiments on supernatural creatures, likely to make the US more powerful.
One of the titles Glory's minions call her is "The Shining Light". She's also blonde-haired in her human form.
Darla too, though more so on Angel where she features more. She's a blonde who is usually dressed in high fashion outfits in bright colours. When she is resurrected on Angel, she becomes a vampire again while wearing a pure white dress.
This is touched on in Carnivàle, as there seems to be no moral dimension for being the Creature of Light or the Creature of Darkness; the latter just seems to spread calamity around himself whether he wants to or not. The current Creature of Light is a decent, albeit extremely reluctant guy, but his predecessor is ruthless, manipulative and cruel. Interestingly, he's not beautiful in the slightest, despite being associated with Light, and prefers to hide behind a curtain or make himself invisible to keep the shroud of mystery around himself.
Samson also mentions it in his pilot monologue: "...A false sun explodes over Trinity..." This is a reference to the Trinity Test of the first atomic bomb (a perfect Real Life example of this trope).
In season 3, Wilson Fisk wears predominantly white three-piece suits after he is released from prison, just like he does in the comics.
Vanessa Marianna predominantly wears white and gray shades of clothing. Then in season 3, upon her return from exile abroad, she orders the murder of Ray Nadeem.
The Defenders (2017): Amongst the Hand leaders, Alexandra and Sowande prominently dress in lighter colors, white being the most prominent. Sowande, who runs a gang that recruits desperate black men from Harlem to do the Hand's dirty work (and then kill them when they are no longer useful), is even nicknamed on the streets as "White Hat" owing to his white wardrobe.
The Tarrs in Defiance. Like all Castithans, they have white skin and hair, as well as golden eyes, dress all in white or light grey, and have an entirely white house. However, they're basically the town's equivalent to the Corleones. The Castithans themselves also count; when they led the Votan they kept the other races in subservient positions and attempted genocide on the Irathiants, herding them into caves and then gassing them.
The Time Lords, Depending on the Writer, and the Doctor even more so. Half the time he's being portrayed as Jesus, half the time he's committing highly dubious acts without actually realizing he's doing something wrong. His perceived morality varies from Doctor to Doctor, but should never be deduced from his manner and face.
The Daleks have dabbled in this on a couple occasions.
"Midnight" has the light be literally killer. Life is thought to be impossible on Midnight's surface, which raises the question: Who's that knocking?
"Flesh and Stone": The crack in time that appears in the wreck of the Byzantium emits bright white light with the power to retgone whatever it touches, and people looking at it feel weird and sick.
The antagonist in the Farscape episode "Crackers Don't Matter" wanted Moya to generate as much light as she could, and used hypnotic patterns in the light generated within the ship to set the crew against each other. We don't find out what he wants the light for, only that it has something to do with what his species wants and they seem to be a threat to everyone else (even though, after he's killed, we never see anything like it again).
House Lannister deserves an honourable mention. A smaller house of Blondes from the sunny south that dons the very heroic colour scheme of red and gold and have a lion in their crest would have easily passed as the good guys in any Anglophone High Fantasy story (especially when contrasted to the rugged, gloomy-looking, black-favouring Starks)... instead of the dysfunctional, incestuous, backstabbing schemers that they actually are.
The Red Woman preaches the faith of the Lord of Light, which for some reason demands sacrifices in the form of burning people alive, uses shadow magic and ominous threats and rather fanatically insists on a "one true god" while people in Westeros speak of old and new gods and seem fine with people believing in one or the other.
White Walkers are not really cool guys.
Light seems to be a major theme of Heroes villain Adam Monroe, even after he becomes a Fallen Hero. So much so that the episode where he is killed is called Dying of the Light.
In one of the Season 6 'Immortal of the day' episodes of Highlander: The Series, the villain is the head of a global charity organization, always seeking donations and preaching hope, charity and mercy. When he ambushes the main character in a carport with two henchmen, this bit of dialog happens:
It wasn't played up a lot in It's Always Sunny in Philadelphia, and it was a role in Charlie's play, not his actual persona, but this kicks in when you realize Dennis of all people was cast as Dayman in Charlie's play/demonstration of his memories of being implicitly molested. Dayman himself isn't evil being "a master of karate and friendship for everyone" (that would be Nightman), but Dennis is the person playing him.
The main villain of Kamen Rider Kuuga is N-Daguva-Zeba, whose human form is a teenager dressed completely in white and whose monster form is basically a white version of Kuuga Ultimate with golden armor. His goal is to release the Ultimate Darkness that will corrupt all of humanity, and he will kill members of his own species that he deems unworthy.
Kamen Rider Kiva has the white armored Kamen Rider Ixa, who is modeled after a Knight Templar. The two primary users of this suit, Keisuke Nago and Iritate Kengo, behave like a Knight Templar and a Jerkass respectively. In Nago's case, he indiscriminately killed a Fangire despite said Fangire's desire to live peacefully among mankind, while Kengo is a little bit too eager to take Wataru's life, despite them previously being friends. They both get better through Character Development though.
Kamen Rider Wizard has The White Wizard. At first, he actually seems like a good guy and a person Haruto looks up to, but later down the track, once he shows his face to Haruto, he shows this trope, or at least show that Good Is Not Nice by injuring one of his allies into a deep coma and kidnapping a kid who refused to become a Wizard. It is eventually revealed that he is also Wiseman, having manipulated both sides for his own goals.
Several characters in Kamen Rider Ghost have the power to transform into the white and gold Ganma Ultima form. None of these characters are good guys.
The Light Fae in Lost Girl are only good by comparison to the Dark in that they have some rules about feeding off humans. One of thier leaders, The Blackthorn describes as much in the episode: I Fought the Fae (and the Fae Won)
"Humans are food. We eat from them or we die. Now the Dark Fae, they tend to kill for pleasure, not just need...We're more like your Native American hunters. We respect the kill. Won't over-hunt. Don't eat the young."
The Big Bad in 'Neverwhere'' is the angel Islington, who (at least in the original TV miniseries) wears a white robe and lives in a chamber filled with lighted candles.
That episode of Nikita where Alex was interrogated using a mind altering drug and she sees her evil self "Alexandra", representing what her life would have been if she had never met Nikita. Alex wore black jogging pants and sweat shirt while "Alexandra" wore this pure white sable fur coat.
Raised by Wolves (2020): The Mithraic religion apparently worships the god "Sol" and has a sun as its holy symbol. Their prayers frequently reference light. However, everything we learn about their beliefs suggests that it's a cruel and merciless religion.
The final seasons of Stargate SG-1 saw villains in the Ori, ascended beings posing as gods (fire gods, really, but they do a lot of light stuff) and trying to convert the Milky Way galaxy to their religion (Origin) so they can use their collective faith to power-up and take out the Ancients. Their religion seems pretty Christianity-inspired, including having their own holy book (The Book of Origin) and inducing immaculate conception in a major character.
However, the Ori fire motif was eventually contrasted with the soft-white light of the Ancients, who also inserted the concept of "fire is evil" into almost every human culture.
In the fourth season, a beautiful, optical illusion-y light was used as an "opium chamber" by Goa'uld. It accidentally snared the main characters after its former users were gone. Although it wasn't the light itself that caused it, the device emitted radiation. The light was just "entertainment" for while the Goa'uld were stoned.
An episode of Star Trek: The Next Generation had Data and the Enterprise computer infected by a program from an archeological artifact, forcing the ship's crew to play out an ancient ritual of a sun and moon exchanging places in the sky—from day to night, in this case. The ritual depicted the soothing, gentle moon convincing the harsh, burning sun to leave the world in peace for a time, to keep the sun from destroying everything.
Supernatural makes a point out of doing this with all the angelic characters featuring from season 4 onwards:
Early in the series, an "angel" actually the ghost of a priest made people commit murders for the sake of considering them evil. He manifested himself surrounded by light, something unusual for a ghost. Played with, as all the people he killed fully deserved it, and the ending implies that the "angel" was right about his murders being God's will.
Contrast the Winchester's angelic ally Castiel with Uriel in "It's the Great Pumpkin, Sam Winchester!" Uriel is fully willing to destroy the Adventure Towns that Sam and Dean have stumbled upon to stop the demonic baddie of the week from being raised (and a seal to the Big Bad's prison destroyed in the process), and he openly refers to humanity as "mud monkeys." Notably however Castiel would have helped destroy the town if ordered to, it's just he would have felt bad about it.
There's also Zachariah and his lackeys. At first, they just seem like smug, superior Jerkasses. And they are. They also want to set off the apocalypse. Or as Zachariah called it, "A cosmic enema." Zachariah also has another wonderful moment later: When Michael needs consent to take over Dean's body, Zachariah gets persuasive. Not content with giving Dean stage 4 stomach cancer and ensuring Bobby will never walk again, he cheerily announces "Okay, then let's get really creative. Let's see how Sam does without his lungs."
Zachariah does mention, however, that heaven's plan was being kept secret from the "grunt" angels, implying many of them wouldn't have gone along with it if they had known.
In the season 4 finale, the ending makes a large change as it fades to white instead of black. Guess who's shining radiance is approaching? Lucifer. Also, in the flashforward episode, Lucifer in Sam's body wears a perfect white suit and shoes.
Remember the Trickster? Liked teaching people lessons in very cruel ways, stuck Sam in a time loop and killed Dean every single day? He's the Archangel Gabriel. And he's on their side.
Crowley reminded us early on that Lucifer is an angel. However, Lucifer only created the demons (from human souls) to prove to God just how debased humans really are. Lucifer himself feels nothing but contempt for the demons.
Naomi is attractive, has a somewhat cold, but brightly-lit office and is very much a prim angel. She is not really any nicer than Zachariah, just not as obvious about enjoying cruelty.
Most demons have Black Eyes of Evil and appear when not possessing someone as thick black smoke. However, certain demons who hold a position of power within Hell have unique eye colours: Azazel has dark yellow, and Crowley has blood red but Lilith, the very first demon, has eyes of solid white.
Nakadai Mikoto AKA AbareKiller from Bakuryuu Sentai Abaranger could as well be the poster boy for this trope. He is the white ranger of this series, is a very charismatic and successful surgeon and saved the life of the red ranger of the series by performing an operation on him. This would indicate he is a kindhearted hero who values the lives of others... except he isn't in the slightest, as he stays evil for the majority of the series. After gaining his white ranger powers, Mikoto only uses them for his own twisted entertainment, no matter how many innocent people are hurt by it. His only motivation for this, is because he is bored and misses excitement in his life. He even manages to become the leader of the actual villains, just to alleviate his boredom. This makes him currently the only ranger in Sentai to voluntarily use his powers for evil for the majority of the series. This trope also applies to the villain Lijewel, whose costume has a slight angelic or priestly vibe to it, as well as being predominantly white.
This trope also applies to Mikoto's Power Rangers counterpart, Trent Fernandez from Power Rangers Dino Thunder, but not to the extent as Mikoto himself. Trent pulls his HeelFace Turn much sooner and is only evil because his powers caused him to turn Brainwashed and Crazy. The whole light vs dark thing is turned on its side, with the White Ranger being Trent's Superpowered Evil Side and the Black Ranger being freaking Tommy. The same series also has the Evil White Ranger Clone, who, like it says, is a clone of Trents white ranger form.
Brajira from Tensou Sentai Goseiger is a fallen angel whose true form has four white wings, while his face looks the most human of all the villains. As he is an angel himself, he is able to use exactly the same powers as the angelic protagonists do, only stronger. His ultimate plan involves causing a mass extinction event on earth, so he could remake the planet in his image.