As well as being a huge example of Lawful Stupid, the paladin Miko Miyazaki from The Order of the Stick is an example of this Trope. The gods of that continent might not actually be much better, but to their credit, they did revoke Miko's paladin-ness after she finally went too far by executing Lord Shojo out of paranoia.
In the print-only book Start of Darkness, according to Redcloak, the gods made the Always Chaotic Evil races such as Goblins, Orcs, Kobolds and such as XP Fodder for their followers to kill and level up, thus getting stronger.
Zoophobia's Adina is literally a glowing angel, who takes it upon herself to destroy those who she deems to be sinners.
The Ivory Veil of Antiheroes is an organization of paladins and allies that the paladins don't lose their paladin powers by associating with assembled by a trapped evil demigod and used as his personal army.
Dominic Deegans Lord Siegfried "Siggy" von Callan falls neatly into this category. A Royal Knight of the comic's kingdom, and one of the most masculine (and arguably, prettiest) characters in the comic, Siggy also happens to be temperamental, violent, and a raging racist cheerfully capable of hanging innocent, nature-loving Orcs from adolescence.
This is also something of An Aesop in the "Storm Of Souls" Story Arc, which goes out of its way to state that Light, Law, Chaos, and Darkness can all be negative forces if one gains too much of an advantage. The Hero is, therefore, the Champion of Balance. He still fights the Avatar of Chaos and Darkness because he was the one messing things up at that point, but his predecessor fought against abuses of Light and Law in flashbacks.
In fact, Raf Malkish, the previous Champion of Light and Law, was willing to kill the family members of his followers to create a Acibek, a Golem of Law. The first thing Acibek did when he was activated? Expose Raf's actions in disgust.
In the recent Orc Lands saga, Dominic explains that in Orc religion, Ice represents good and Fire evil. When his companion pointed out that it was an odd thing to base religion on, Dominic pointed out that orcs felt the same way about humans using Light and Dark. What make Light good and Dark evil?
While the Necromancers of the Shintula clan, who channel the black Power of Death, can be quite violent and brutal and are not known for kindness, they are mostly desperate and try to save the land. The Bikta, who channel the white Power of Life, are however Knights Templar of the worst kind.
In this strip of Fans!, after the 23-sider of power is recreated, Tim spells out this trope for Ally.
Blanc from Adventurers! had white hair, wore all white, and shot blasts of white energy.
The main character Danny of Chess Piece uses Holy, but is a sadistic, amoral Evil Prince who may or may not have killed his great-grandfather. Ironically, in spite of this, (and his Take Over the World scheme) a short time when he ruled the country while his dad was gone saw him to be a fair ruler. Go figure.
That's because it's purposely kept ambiguous on what he plans to do with the world once he takes over it.
You know how Dr. McNinja recently got a new motorcycle? That motorcycle is actually a polymorphed Unicorn, and ever since he got it, the Doc has been acting more and more erratically and amorally. Coincidence? You decide.
Oh, and it was recently revealed that the previous owner of the unicorn bike had gone on a bloody killing spree. That owner? An elderly antiques dealer who had no memory of even owning the thing. And as soon as he does remember, he's mysteriously murdered. Yeah...
Recently brought to a head when King Radical reveals that Sparklelord is an Evil Overlord and describes him as a combination of Genghis Khan, Adolf Hitler, atomic bombs and Seabiscut.
More recently revealed is that King Radical was lying through his teeth, the motorcycle is only a little worse than he is. He then rides away on his own magic motorcycle, laughing.
Rachel from Tower of God. Baamnote whose name funnily enough means Night often refers to her with light metaphors and when they first met, light shone down on her as if she were in a religious painting. Add to that her biblical name, her gold eyes and matching hair and you'd think she'd be a good guy. You'd be wrong. She is in fact just a normal girl of very low birth who wanted to escape her life. When Headon strikes a deal with her to sacrifice Baam to ensure her way up the Tower, which would grant her a single wish, she accepts. Later, she kills Baam, or so she thinks, and gets taken in by his new best friend Koon's team, playing a disabled girl.
Shadowgirls's main villain, Mother Hydra. In human host she/it has light-based powers, as a Foil to protagonist's shadow-based. It doesn't help that her host is blonde girl who happens to speak in golden speech-bubbles.
In Misguided Light, God thinks a certain Nazi war criminal can be trusted with divine powers, including the abilities to control light and enslave people.
Kore from Goblins is a paladin - how he remains a paladin is yet to be revealed - who kills supposedly Always Chaotic Evil races, as well as anyone who associates with them, voluntarily or not. Knight Templar does not even begin to cut it. His magical aura looks like angel wings made of tortured souls.
Specifically, its implied to be the souls he killed, chained to his back.
Three of Homestuck's characters are Heroes of Light, and they all play with this trope a little. Rose, as the Seer of Light, touches it by proxy, preferring to use dark-based magic (thus playing into Dark Is Not Evil), while Vriska, the Thief of Light, is..."ambiguous". Vriska is contrasted to Aranea, a Sylph of light (combining healing with her aspect who's well intentioned and willing to sacrifice anyone in a plan to fix the paradox-space.
"Light" in the Homestuck mythos is actually the Aspect of Fortune, not goodness or literal light, which partially explains this.
Eridan is the "Prince of Hope", yet has genocidal ambitions. He gets a white wand that lets him shoot blasts of light, and becomes decidedly a Not-So-Harmless Villain by using them to blind his romantic rival and kill his love interest, an egg needed to revive his race's future chance of survival, and the friend in charge of keeping it. Later it's revealed that the Prince class is one who destroys their Aspect or destroys with it.
In fact, one of the posters on the MSPA forum has noticed that most "threats [to the trolls] feature or involve lights or brightness" (Vriska's fairy sparkles, Eridan's "white science", vampire Kanaya (the troll undead are associated with the sun, and Kanaya glows), the way Terezi becomes blind, and Bec Noir's white-green lightning.) "All pretty grim and chilling for a nocturnal race—very well-constructed".
Feferi is the Witch of Life, the life aspect generally bringing healing powers. Assuming her ancestor, the ImperialCondesce, has the same attribute (she was able to extend another troll's life-span, after all,) then she definitely qualifies for this.