Vampire: The Masquerade has several levels of standards, especially considering the players are playing corpses repeatedly engaging in what is essentially cannibalism. Most clans despise the Sabbat (for being Ax-Crazy nutcases with seemingly no regard for the Masquerade), the Giovanni (for being incestuous necromancers) and the Setites (for being dealers in generic sin). These in turn despise the Ba'ali (for being worshipers and servants of powers wanting to end existence). And certain sub-factions of the Ba'ali despise the other subfactions.
The Ventrue (in the Old World of Darkness) are the Blue Blood rulers of the Kindred, and the highest enforcers of the standards expected within the Camarilla.
Vampire's Humanity mechanic allows players to invoke, invert or subvert the trope any way they choose. But they can never really avert it because of the long-term gameplay impact, which reinforces the trope as an essential theme to the game. "Monsters we are, lest monsters we become."
In some ways, the Virtues of Compassion and Self-Control mimic this. Low Compassion or worse, its opposite, Conviction means you can do horrific things without even suffering the slightest pang of guilt, but high Self-Control keeps the Evil in check - if you had low Self-Control you'd be Ax-Crazy, leaning towards Blood Knight.
Many of the more inhuman moralities have this trope in full effect. Two examples would be the path of Lilith and the path of the Night. Those on the path of Lilith believe that pain is a good thing, and will happily kidnap and torture people for no better reason than a passing kindness of making them more jaded and realistic. Murder to a lilin is seen in exactly the same light as to a follower of Humanity; "dead mortals feel no dread". The path of the Night views vampires as agents of hell. They choose a victim, investigate them until they find a sin, however minor, then torment and traumatize their victim with the aim of making their life a living hell. Emphasis on living once again, killing is still wrong.
The Guide to the Sabbat sourcebook encourages players to play Sabbat characters who go about murdering, raping, torturing, and generally raising Hell, metaphorically at least. But if you literally try to raise Hell...the book mentions in several places that demon summoning is a Bad Thing, the GM is under no obligation to allow the players to do it, and if they do, the GM should be willing to drag their characters off to Hell on a whim.
And in-universe, the Sabbat, who make a point of being pure and utter monsters, with no regard for human life and no care for anyone's safety, will haul you out of your haven and throw you into acid if they find out you're messing around with demon-invoking.
Similarly, in Vampire: The Requiem, despite being vampires, the Kindred still have depths they refuse to sink to.
Draugrs in 1e are vampires who have totally given up every remaining scrap of humanity. They come in two varieties: utterly evil, insane monsters who can at least think, and mindless beasts driven entirely by their dominant Vice. Vampires hate Draugrs in general, but the mindless type get it the worst. Especially bestial Draugrs driven by Lust, who are noted as A: sparking city-wide death-hunts when their presence is revealed, and B: being one of the few times vampires can actually feel heroic.
Belial's Brood are, similarly to the Ba'ali above, hated for being vampiric demon-worshippers who consider it a sacred duty to grind their humanity into the dirt and spread the power of their infernal masters.
2e has the historical Children's Crusade, an entire conclave of juvenile vampires, who were eventually hunted down and destroyed for reaching a level of cruelty and depravity that even other vampires found intolerable. They were willing to work with the Strix, a species of shadowy demon that hates all non-Draugr vampires for being too human.
The 2011 Grey Knights codex has an Inquisitor who will happily call in orbital strikes on his own men. It makes the shot perfectly accurate. Then again, given that the supposedly holy Grey Knights butcher nuns and use their blood as a holy ointment in this same codex, the "good" and "pure" seem far worse than the evil.
Khorne, the Chaos God of rage, murder, and general Ax-Crazyness will fuck you up if you try to present him skulls of the defenseless. Although this is less because he has standards and more because he wants skulls of Worthy Opponents (trying to present him a bunch of baby skulls would be cheating). Similarly, Khorne loathes the use of trickery and deception. As a result, he's the only Chaos God in Fantasy whose followers cannot use magic. Similarly, in 40k, none of his followers can use psychic powers (even his daemons) and need to resort to more conventional (in comparison: a plasma cannon is anything but conventional otherwise) methods of dealing ranged damage. However, he doesn't have any problems with ranged weapons.
The Redemptionists, a splinter sect from the Imperium dedicated to burning things even remotely heretical, are so deranged that the Imperium is frightened by them.
This crops up any time the followers of opposing Chaos Gods butt heads. For instance, Tzeench will have no compulsion against setting up schemes that cause untold billions to suffer near-eternal agony if it fosters positive change for (at least some of) his plans, but cannot stand the way that Nurgle just makes everything rot and fester and corrode without any greater end-game. Similarly, Khorne is the god of bloodshed, rage, and sacrifice, which means that followers of Slaanesh (narcissists, hedonists and rapists) are anathema. Khornates even pull an unintentional Villainous Rescue against Slaaneshi cultists in an Imperial-viewpoint novel.
Along the same vein as the above example, Kharn the Betrayer is so Ax-Crazy that other Khorne Berserkers refuse to associate with him. The thing about Kharn is that he's not just an unstoppable murder machine, he's an erratic, team-killing unstoppable murder machine. In the novels involving him he's actually surprisingly skilled at navigating Chaos's internal politics by playing up his Psycho for Hire reputation; he'll then wait until the moment where it will maximize his bodycount to betray everyone.
In the Horus Heresy tie-ins, even the Iron Warriors— who committed genocide on their home world to suppress a rebellion, and who are among the most ruthless and bitter siege troops in the setting— think the Emperor's Children have become badly fucked-up and a disgrace, and they are appalled by Mad Doctor Fabius Bile's... experiments on other Space Marines. At another stage, Konrad Curze, a murderer who considers psychological cruelty a useful tool and spends an entire book attempting to psychologically break one of his brothers, describes the Word Bearers' Possessed Marines as being "rancid" with corruption.
The Iron Warriors had another moment during the War of the Beast; not only do they set aside their grudge with the Imperial Fists long enough to ally with the Black Templars against the Orks, they are disgusted to find that the orks have drugged up hundreds of human slaves to serve as "cattle" for the greenskin hordes.
The Necrons are basically genocidal Egyptian robotskeletons. But even they are creeped out by the Necrons known as Flayed Ones and the nihilistic Destroyers. They also have a rule against deploying Deathmarks against any foe not deemed "dishonorable"— which usually translates to other Necron dynasties. (Non-Necron enemies are fair game though.)
In the fantasy setting of Warhammer, the Beastmen are a bunch of murderous, psychotic savages who want to spitefully annihilate civilisation and so they have few rules, but one of them is never harm a shaman. This is something that should be told to Gorthor, who actually wore the skins of his rival shamans, giving him a reputation of The Dreaded even among them. His name in Bray-tongue means "cruel".
Also in Warhammer, goblins, a race of comically evil little sneaks who cheerfully backstab, rob, murder, betray, swindle and even eat each other with minimal provocation, think hobgoblins are treacherous bastards and will shoot them on sight.
In the Eberron D&D setting, evil is not dependant on one's personality or goals, but rather, on how much one is willing to compromise. The queen who wages a bloody war to conquer the kingdom is good while the king who tries to maintain peace and security is evil. Why? Because she has standards; she wouldn't stoop to underhanded assassination plots, for instance. The king? He'd throw puppies into a woodchipper to achieve his goals. Evil does not have standards in Eberron.
Many of the big-name villains of the Ravenloft setting have standards, even if their other crimes overwhelmingly outweigh them. Strahd von Zarovich, though he preys upon them himself, vigorously protects his Barovian subjects from outside threats; Dr. Mordenheim has treated the injured even if it didn't advance his research to do so; Azalin takes his obligations as a king very seriously, despite the fact that he despises his kingdom.
There are also different degrees of evil among the darklords. Azalin has nothing but contempt for the cruel tyrant Vlad Drakov, the lord of the neighboring Falkovnia; same with all the darklords of the realms who border Falkovnia, actually. And the ironic part is, Drakov has no supernatural powers at all. He's fully human. But his cruelty is greater than almost any darklord who does.
In the Pathfinder setting, devils are bent on dominating all that is, bringing order to the universe through tyranny and treating mortal souls as tools, slaves, and currency. Demons enjoy desecrating the flesh and warping the souls of mortals, seeing them as playthings. Both devils and demons will put their differences aside and work alongside angels to stop daemons, who only want to eat and destroy mortal souls.
Rovagug, God of Omnicidal Mania, tends to invoke this among the other gods. Asmodeus (God of Tyranny), Zon-Kuthon (God of Envy, Darkness, and Loss), and Lamashtu (Goddess of Madness, Monsters, and Nightmares) are opposed to his being released, largely because hey, not even they benefit from the end of the world.
The empire of Cheliax is ruled by the Thrice-Damned House of Thrune, who sold their souls to Asmodeus in order to gain power. The current monarch, Queen Abrogail II, has a Pit Fiend for an advisor. This would be scary enough, but it's indicated that his primary job is to keep her from acting on her more evil impulses. That's right, a literal servant of Hell, of the most feared race of devilkind, has to keep Abrogail from going too far.
This is how some people view the Lawful Evilalignment in Dungeons & Dragons. He may kill babies, assassinate kings, and plot to take over the world, but many a Lawful Evil villain will never engage in wanton slaughter to no purpose and will never break his word. That being said, there is nothing to prevent a Lawful Evil from engaging in Pragmatic Villainy and finding minimal pretense to do the above ("I won't slaughter these villagers For the Evulz, I need living space for my more important countrymen"). Furthermore there is nothing to prevent the Neutral Evil and Chaotic Evil characters from having standards themselves. And the biggest flaw of the Lawful EvilEven Evil Has Standards view is that Devils, the literal embodiments of Lawful Evil pre- and post-4th Edition, do all these things without the need for standards.
The Drow, the infamous Evil Counterpart of the Elves and Eladrin, are brutal, fascist conquerors whose society is based around lies, deceit and betrayal, are prone to brutal infighting, and live by the unpredictable whims of their batshit insane goddess. And yet, even they are disgusted by the horrifyingly insane Derro, so much so that they're willing to put aside whatever evil plot they're currently concocting to put a stop to the Derros' own plots.
The Al-Qadim setting encourages this trope with regards to honor, citing examples from the Arabian Nights and Arabic folktales in which a variety of murderers and thieves hold the Sacred Hospitality rite of taking salt to be an unbreachable code.
Numerous examples occur in the Elder Evils guidebook, where evil beings side with the heroes to oppose the Eldritch Abomination featured in the scenario, seeing what the creature is doing is something they cannot allow. The most extreme example is given in the backstory for Zargon, which claims that Asmodeus sided with the forces of good to halt the Elder Evil's first rampage. (The book does suggest, however, that this may have been at least partially a case of Pragmatic Villainy on Asmodeus' part, seeing as Zargon was the former ruler of Hell who he had overthrown, and he did not want the guy around.)
When Dungeons & Dragons 4th Edition pared down the Character Alignment system, this became the primary way of differentiating between Evil and Chaotic Evil. An Evil character can still be a complete and utter monster (see the Devils mentioned above), but usually their vision for the world is relatively tolerable. A Chaotic Evil character, on the other hand, has such horrific goals (however loosely applied) that even Evil characters are horrified by them. There's a reason the main holders of the alignment in 4e are Demons and Slaadi. This means a Chaotic Evil villain is the kind of thing that can make Good, Unaligned and Evil characters team up to beat its head in.
Scion has this in regards to Loki. He initially backed Hitler's rise to power in Germany in the hopes that a united Europe would allow him the power needed to stave off Ragnarok (it makes sense in context), but he was unaware of the Holocaust and would not have condoned it. After World War II, the Nazi high command faced the greatest punishments Hel could deliver... but Hitler's soul never appeared in the Underworld.
The authors do note that while some gods aren't exactly the nicest of individuals, they still do care for humanity on some level. Even the most bloodthirsty of the Aztec pantheon would not callously slaughter huge numbers of mortals For the Evulz. This is what sets apart the Titans and the darker Gods.
In Rifts, the Obviously Evil Coalition States is lead by Emperor Prosek, who will cheerfully plunge his nation into pointless, horrific wars for the sake of power. He is absolutely ruthless when it comes to destroying non-humans and magic users. He even has a facility used to create mutant animals to be used as canon fodder. However, genetic experimentation on humans is strictly forbidden.
The "Aberrant" character alignment is essentially this — an Aberrant character is unambiguously evil, but at the same time follows a strict personal code of ethics. They may (for instance) kill without a thought, but never without reason, and are disgusted by characters of the "pure evil" Diabolic alignment.
In The Dark Eye, those who forge a pact with the demon lord of tyranny and vengeance are despite their evil will direct enemies of the servants of the nameless god. The demon lord's demon subjects may even demand this attitude of their human "masters" no matter how well they are controlled.
The Hochog in Stars Without Number believe everything comes down to reputation, and will do virtually anything to increase the reputation of their pack without showing any kind of regret. A Hochog will gladly devastate your planet and never feel a shred of remorse. However, they also strongly disapprove of any kind of cruelty. Many a crime boss has woken up without his Hochog mercenaries and missing rather a lot of blood after getting a little too "enthusiastic" with a punishment.
Although the Ashwood Abbey are noted mostly for being depraved deviants who rape, torture and even cannibalize the monsters they hunt, which incidentally means most other hunters despise them, the Spirit Slayers sourcebook mentions that "nobody sober" would admit to their actually skinning the now human corpses of slain werewolves to make clothing, rugs or other trophies out of them.
The Ashwood Abbey are also on the receiving end of this from Beasts, creatures with an innate hunger for human fear, who view the Abbey as utterly despicable and go out of their way to make the hedonists' lives as miserable as possible.
The Promethean Brotherhood, a bunch of magic-envying hunters whose whole compact is dedicated to the idea of using Human Sacrifice to steal magical abilities from mages or anyone who has magical power, are noted as regarding the branch of their compact dedicated to deducing how to make the ritual more reliable with disgust for the things they do in pursuit of their goal, which include eating hearts, drinking blood, and wearing peoples' skin.
The Night Watch are comprised of gangbangers, petty hoods and other "ghetto trash" who decided they couldn't stand having vampires running around in their neighborhood.
Almost none of the Hunter organisations, even the ones who are utter bastards, are particularly fond of Heroes from Beast: The Primordial, who are more often than not glory-obsessed egomaniacs with no real concern for collateral damage.
The New Belt Pirates of BattleTech are, as might be expected, opportunistic raiders, amoral scavengers, and general scumbags, but even they didn't want to have anything to do with the Word of Blake.
All vampires are bloodsucking undead nightmares (except Wendigo who are cannibalizing undead nightmares), but even they can't stand the nightlords, who are essentially a one man mafia of rape, cannibalism, enslavement, and random slaughter For the Evulz. Furthermore, most of them hold themselves in a higher moral ground than Primal Vampires.
Witches are all dead chicks who were resurrected by a pagan god in exchange for eternal servitude and the occasional sacrifice. But even The Host of Corpses and The Host of Fire are uncomfortable with the Host of Demons, who kidnap, torture, and kill children to gain more power.
All ghosts feed on human emotions and usually manipulate them into feeling that emotion more often. However they are not willing to stomach the Creeping Reapers who kill and eat other ghosts for more hold.