And for what? It's been many years, Yet the screams of the vanquished still ring in my ears. And for what? I've blood on my hands. I wait for my place in the halls of the damned. And if I could go back and make my amends, I'd make all those mistakes again. I'd kill every last one of those bastards, my friend!
There's a common stock character, the grizzled old guy with a wealth of experience who'll share his views with a travelling band or bold young rookie. There's no more adventuring for this old timer. He's seen it all, done some good, maybe done some bad; but overall he has earned the right to put his troubles behind him in his twilight years. He may be the Cool Old Guy or Old Master. Perhaps if life really got him down, he'll be a Grumpy Old Man, and if someone manages to rub him up the old way you'll see he's a Badass Grandpa, but it's unlikely since some haunting experience makes him disinclined to take up arms again.
This is not that guy.
The Retired Monster may look like that archetype but his past is full of evil and atrocity and he's okay with it. In fact, he caused most of it. When you first see him, he'll come across as Affably Evil; he'll also have experience and advice that he might give out to a young hero, although possibly the best he can do is "You should stay away from people like me". However, he'll be creepier than the other guy, and he'll tempt the young ones, giving them advice more on the cynical side of the Sliding Scale of Idealism Versus Cynicism. You see, he's not doing any gross evil acts now — he may not have done so much as run a red light in the past ten years — but that's only because he's tired. As the backstory of this character becomes known, we learn that they kicked the dog a number of times, perhaps took a hopscotch over the Moral Event Horizon, only stopping because for some reason they got sick of it.
Perhaps he finally came out worse for wear after a run-in with the guy who's now The Obi-Wan. Maybe he was caught and sent into exile and now has at least enough fear of the authorities to not put a toe out of line. Then again, often, they have just literally retired, saying "I'm too old for this" and using their pension fund of Nazi gold to support a life of margaritas on the beach.
They've never said sorry, or at least never meant it, there was no Heel-Face Turn and they are not The Atoner who'll help to make up for some wrong. No, they'll just sit back, but if a character underestimates their evil, if they think that because they aren't as bad as the more active monsters, that they're OK, they may get a horrid reminder of what the Retired Monster is capable of.
Monsters who don't retire, or come out of retirement and continue to be evil in old age, can become Evil Old Folks. Sub-Trope of Karma Houdini, due to the fact that very few of this type of character are found in jail. Compare the Retired Badass, one of several good counterparts, and the Retired Outlaw, which may occasionally overlap. Contrast The Atoner.
Hard to say, since, by the end of it, he was depicted as something of an atoner.
Hartmann probably fits this description well...
Madara from Naruto went into hiding after defeat by Hashirama. When he took in Obito, he was a one-eyed, decrepit man kept alive only due to a life support system he had jury-rigged from an experiment. He seemed largely uninterested in the outside world and was even helpful. In fact he had spent the last few decades preparing his big comeback and Obito was just the final piece in his plan.
Danzo is suitably monstrous and pretends to be retired from his duties outside of acting as an advisor. Most of the cast knows he's still running Root and tasking them with black-on-black ops. He comes fully out of retirement when he temporarily becomes Hokage, only to have all of the enemies he's made come out of the woodwork when he steps out of Konoha.
Despite settling down on Earth and attempting to save it on several occasions, Vegeta of Dragon Ball Z has never explicitly been shown to express any guilt, angst or shame for his decades long life of murder, tyranny and genocide.
During the Buu saga, he makes this speech about how he wanted to go back to the days when he was a cold-hearted, ruthless brute who thought of nothing but causing pain and suffering to others. An episode earlier, when he becomes Majin, he proclaims to the Supreme Kai, "No! I am not innocent!" He knows he was an evil monster once and wishes to let that monster inside him lose again.
This is, of course, because he feels he's gone "soft" and that he could—and should—be stronger than he is. By returning to the old state of mind, he believes he'd be able to use his full power. There is a bit of a subversion however, ironically enough, when Porunga was asked to revive all those on earth who aren't pure evil, Vegeta is resurrected. He then appears genuinely stunned at just what that means.
Aya's mother in Master of Martial Hearts. A former Dark Action Girl, she used to partake in a girls-only Street Fighter Expy, under the direction of her husband-to-be. Doesn't help the fact that the girls she beat up and defeated ended up tortured, maimed and sold into sex slavery (Like it happened to Natsume's Cute Mute mother). However, with the Platonic Heart closed for the time being, she settled as your average, if slightly overprotective mom, raising her daughter. Under the mask, she's still as plucky and dangerous as she used to be.
Lucy from Elfen Lied. In the years'-long era between her killings of Tomoo and his subordinates and her capture by the Diclonius Research Institute, she killed Kouta's sister and father out of a hissy fit of jealousy when Kouta lied to her about his cousin's gender (even if he explicitly told her about his cousin's real gender, someone was bound to be dead, anyway) and caused a series of heart attacks across Kamakura while infecting males with the Diclonius virus. While she does feel guilty (deep down inside) about the murders of Kouta's father and sister and tries to atone for it, when she comes out of retirement (by slaughtering several Diclonius Research Institute personnel), she proves herself that she's still excessively murderous.... not that those Research Institute personnel didn't have it coming, mind you. Yeah, it's that kinda series, where being locked up in a Tailor-Made Prison that frankly has "Nazi Concentration Camp expy" written all over it is bound to mess one up (more than what she already was). She does get better at the end, via limiting most of her murders to people that actually deserve it.
Claimed by Evangeline in Mahou Sensei Negima!. Noble Demon attitude aside, it's actually not entirely incorrect: She has killed people and shows no remorse for anything she's done in the past.
Tomoe from Kamisama Kiss used to be a ruthless demonic murderer, bandit/warlord before the Land God Mikage recruited him to be his familiar. He still isn't exactly a nice guy (just ask Kurama, Mizuki or anybody else who has ever pissed him off) and sometimes dreams of going back to the 'good old days.'
Flit Asuno becomes one of these by Season 3 of Mobile Suit Gundam AGE. A former Fallen Hero and Dark Messiah who took control of his country in a military coup at the end of Season 2, Flit's not sorry about having anybody who disagreed with him executed, continues to hope for a Final Solution to the Vagan problem, and after being dragged out of retirement, proves he's just as ruthless and brutal as he ever was.
In Black Lagoon, Dutch discovers that their employer on the submarine job is actually a retired SS officer who set them up on a collision course with the Neo Nazis in order to test the Neo-Nazis. Since they all died, he considers them to have failed the test.
In the Prototype comics, the anchor Alex's seemingly kindly father figure is eventually revealed to be this. Alex.....doesn't take it very well
Paul Moses from Red by Warren Ellis. At least at the start of the story. His last line is: "I'm the monster. Do your best."
The original premise of Nexus was that the title character was compelled by alien forces to seek out and execute mass murderers. Some actually were repentant or just old and tired, but the alien forcing Nexus to kill them didn't care. Nexus was not at all happy about this.
In Preacher, Gunther Hahn, the Angel of Death and, at the end of the story, the Saint of Killers all qualify.
A future, senile version of Doctor Doom appearing in X-Factor has faded away into a quiet life in his empty, decaying castle attended to by robot servants. But he still builds the occasional Death Ray in his more lucid moments.
In Archie Comics' Sonic the Hedgehog, the immortal and ancient villain Mammoth Mogul eventually decides that trying to conquer the world while Sonic is still around to fight him is way too much trouble. The villain is content with running a casino while waiting for Sonic to eventually die.
One of The Fantastic Four's oldest enemies (the first, in fact) was the Mole Man. After years of trying to gain revenge against civilization for neglecting him by leading the giant beasts of Monster Island against cities, he decided he was tired of it, and retired from villainy. (For the most part. While he's had enough of being in the limelight, things tend to happen that drag him back into it from time to time...)
In Silence of the Lambs, Hannibal Lecter plays this role, but the cannibalistic serial killer isn't very committed to leaving his days as a villain behind.
Con Air features a rather shockingly congenial former serial killer. Played by Steve Buscemi who pulls off a very creepy performance.
Esteban Vihaio, Bill's surrogate father. He was a pimp who lead a vicious gang consisting of his whores' children, but he's retired as of the movie. In reference to Bill shooting the Bride years before, he says "I would have just cut your face." Doesn't sound so bad compared to what Bill did, but just then he calls one of his girls over to the table sporting a hideous and disfiguring scar running across her mouth. He hands her a hanky to wipe off some drool, then she fetches him a drink. The man is only semi-retired.
Pai Mei, an ancient Kung Fu master with a history of atrocities and bloodshed, who sports an unpleasantly racist and sexist worldview, along with the knowledge that he can do just about anything to anyone without fear, since he is just too tough and skilled to die. Until Elle Driver poisons his fish heads in retaliation for snatching out her eye, that is. Ironically, Bill thinks that he's getting lonely because everybody is too frightened to approach him, and that's why he accepts apprentices he despises, even though it doesn't stop him from abusing them as much as he likes. Even more ironically, despite being a chauvinist who hates Americans, the Bride (an American woman) becomes his best student, and the only one he is willing to teach his most powerful technique to. She even starts to love him like a father, and eventually avenges his death by tearing out Ellie's other eye and leaving her to die in the desert.
Most of the Deadly Vipers themselves qualify. Bill had long retired from assassination work by the time Beatrix caught up to him, electing to raise their daughter instead, Vernita quit outright and preferred to try and build a family, and Budd was just living out his days in a trailer and working as a bouncer. Beatrix herself also qualifies, having a change of heart after getting pregnant and wanting to leave the profession and live in El Paso, though Bill would have nothing of it. The other two members, Elle Driver and O'ren Ishi'i, however, were still active; Driver was still doing professional assassinations and Ishi'i had taken over the Yakuza gangs of Japan.
The porter from The Seventh Seal establishes himself as this with one scene. He rescues a woman from an attacker, then off-handedly mentions that he could rape her, but he isn't going to, because participating in the Crusades has made him bored with rape.
Charlie Barrett in Suicide Kings is a former mob boss who used to have his enemies fed to their own dogs. Now, he's retired. Until he gets kidnapped by a group of rich kids looking to raise ransom money for one of their siblings.
Captain Teague in the third Pirates of the Caribbean film is heavily implied to be one of these. The Brethren Court, who are all pretty badass Pirate Lords in their own right are scared by his mere appearance at the meeting, even though he immediately slumps down in the corner and absent-mindedly begins playing with a guitar. When one of them suggests not following the Code for the second time, one of his strings snaps and he looks up, terrifying them all into silence.
Not to mention the fact that he makes his appearence by shooting another pirate in cold blood.
Anyone capable of hitting someone in the chest from that far with a single-shot musket pistol would humble all around him.
"The Weird" of The Good, the Bad, the Weird turns out to be one of these. basically, part of the reason The Good is hunting The Bad is because he believes The Bad is this notorious bandit known as the "Finger Chopper". While The Bad is a total psycho, it's ultimately revealed that The Weird was the Finger Chopper and The Bad lost a finger to him. This reveal probably has a lot to do with The Weird being an expy of Tuco of The Good, the Bad and the Ugly, and in both cases, the seemingly comic relief character has a rap sheet of some seriously awful crimes.
William Munny of Unforgiven is one of these, in a deconstruction treatment of Clint Eastwood's Western anti-hero roles. While it doesn't seem like he necessary enjoyed killing, in his youth as a bandit, Munny was a cold blooded mass murderer - killer of women, children and even animals. The events of the movie bring him out of retirement. English Bob could also be considered one of these. While at present, he plays the role of Remittance Man and is a sort of celebrity, it's indicated that he was previously employed killing Chinese laborers for the railroads, and the truth behind his gunfighter exploits is that he was a dishonorable Combat Pragmatist.
Helge Klingenfeldt-Hansen from Festen (The Celebration), a retired businessman celebrating his 60th birthday, respected for his wealth and conviviality, and who sexually abused two of his children for years, eventually driving the elder to suicide.
Zachariah Rigsby and his wife from Seven Psychopaths would used to go on cross-country murder sprees, hunting some of the worst of the worst. They even got the Zodiac Killer!
In Apt Pupil, young Todd Bowden discovers his quiet German neighbor is actually Nazi war criminal Kurt Dussander and decides to blackmail him.
The film The Act of Killing follows two gangsters in Indonesia who extorted and killed at least a thousand people - they've now become leaders of a paramilitary organization, but aren't the muscle.
Played with in Urban Legends: Final Cut. In the final scene of the film, Solomon is in a mental institution where, after watching Amy's film, the nurse asks him if he enjoyed the movie. He is wheeled out by another nurse, who is revealed to be Brenda Bates, the killer in the original film, who says that they have a lot in common.
Albert, Death's servant in the Discworld books, seems like little more than a crusty old Jerkass. The wizard Alberto Malich, however, was a tyrannous bastard who ran the Unseen University like a boot camp and happily cursed any Muggles who stood up to him into oblivion, before disappearing while trying to attain immortality by performing the rite to summon Death backwards. Having achieved his goal of immortality in a roundabout way, Albert is actually content just to serve Death and do nobody any harm, especially considering there's a very nasty fate waiting for him if he ever does die.
According to The Onion's Our Dumb World, Argentina is full of retired Nazis that fit this description, who will not shut up about that one time they killed a Jewish girl by hitting her over the head with their rifle.
The german children's book "Mecki und die Sieben Zwerge" ("Mecki and the Seven Dwarves") has a literal one. Mecki, a hedgehog, is send by the seven dwarves to slay an evil dragon who, in a quite civilized conversation, turns out to be pretty evil but too old to go out and raid villages anymore. Well, he is still fit enough to easily kill Mecki if the latter would actually attack, so the hedgehog sets up a fight against a dragon puppet for the dwarves to witness. The dwarves fall for it. In a strange turn of events the dragon happens to witness the fight too - and dies from a shock-induced heart attack.
Soon I Will Be Invincible's Baron Ether. He was the world's first supervillain, and he's committed every crime you can think of, now he's a wheel chair ridden mildly senile old man.
In the Corvis Rebaine series, Corvis, Terror of the East in The Conqueror's Shadow until the Current Monster threatens his wife and kids. The remainder of the book is an illustration in why provoking one of these into coming out of retirement is a really bad idea! In the end, he is content with "merely" being a Man Behind the Man via Mind Control magic.
The Necroscope Saga has Faethor Ferenczy, retired due to death. In this series that is no bar to being an active participant and spends his time being Harry's Spirit Advisor. His one attempt to come out of retirement, does not go well for him.
Of course, he had to leave the Sultan's service for the same reasons that made him fly from Persia: He knew too much. Then, tired of his adventurous, formidable and monstrous life, he longed to be some one "like everybody else." And he became a contractor, like any ordinary contractor, building ordinary houses with ordinary bricks. He tendered for part of the foundations in the Opera. His estimate was accepted.
In Stephen King's novella, Apt Pupil, the teenage protagonist is fascinated by his old neighbor, who took part in Nazi atrocities. His increasing fascination with the old man slowly brings back the monster in him.
Sergeant Bothari in The Vorkosigan Saga is a fairly sympathetic example of this, having a tramatic and abusive childhood which left him with no sense of self, instead mirroring however others wanted him to be. Bothari is undisputably a sociopath, and when under the command of a sadistic officer, regularly followed orders to rape and torture prisoners. However, following a Sudden Principled Stand, he ends up as a trusted bodyguard/ Psycho Sidekick of Cordelia and Aral Vorkosigan, as Cordelia is able to convince him to believe in an image of himself as an honorable soldier- and he doesn't really feel guilt for his past actions, as he sort of convinces himself that they didn't happen. His lack of true remorse is showcased The Warrior's Apprentice, in an incident where Miles had no choice but to let Bothari perform the Jack Bauer Interrogation Technique on an enemy soldier. Miles notes Bothari's unhealthy eagerness to obey this order, and Bothari proceeds to torture the man to death with sadistic glee.
The titular character in H.P. Lovecraft's The Terrible Old Man is implied to be one. Pieced together from the meager hints of the story, he appears to be a former pirate captain who through black magic keeps the souls of his former crew captive in jars on his desk. Unlucky burglars discover the hard way how a feeble, old man with no bank account, who pays for his meager purchases with old gold coins can live quietly without fear of being robbed.
At the end of Timeline-191, Brigadier-GeneralClarencePotter becomes one of these. He's not sorry about any of the things he was a part of—the genocide of the black population, the nuclear destruction of Philadelphia, the torture of suspected spies, or the commission of war crimes. He is, however, old, tired, and fully aware that the Confederate States of America are no longer a going proposition, and settles down to write his memoirs.
Dracula in Season 8. Yes, Dracula. Because he's most likely madly in love... with Xander. Dracula.
Star Trek: The Original Series: "The Conscience of the King". There was Kodos the Executioner, a notorious tyrant who had murdered thousands in a massacre decades before the date of the episode. (The true villain of the episode, however, is his daughter, who tries to kill every remaining witness of the crime - this includes Kirk - to prevent her father from being arrested for it; Kodos dies when she tries to kill Kirk, taking a laser blast meant for him, making him a somewhat tragic figure as his past crimes not only catch up to haunt him but to destroy the one thing in his life he had hoped to keep pure and untainted.)
In one episode the protagonists meet a Cardassian with a similar background, being the brutal camp commandant of a forced labour camp... or was he? Turns out he was merely a filing clerk who had assumed his identity, having been driven mad with guilt for all the atrocities committed there. His goal was to be executed as penance for never speaking out against the brutality, and to shine a light unwanted by the Cardassian government on the atrocities committed.
Garak is a complicated subversion. He was caught and exiled for an unspecified crime (hinted to be some kind of treason or betrayal of the Obsidian Order) and he has a reputation for being a very dangerous man who shouldn't be trusted. However, as the show progresses, it's becomes less clear that this reputation is as cut-and-dried as it first seemed. Eventually, it becomes clear that he's not so much heartless about the past, and he may not easily admit it or apologise for it, but he's carrying at least some guilt about it. His motivation for everything he did in the Order was a bitter and cynical I Did What I Had to Do, and he wasn't above sacrificing his own sense of morality for his job or Shooting The Dog if he had to.
He become a part of the Obsidian Order in the first place because his father, Enabran Tain, was trying to mold him into the perfect operative... and he succeeded, however although Garak has done many morally ambiguous things in his life and was even brought up to enjoy performing Cold-Blooded Torture, he doesn't feel that good about it in retrospect, and it's clear that the main reason why he did what he did was because of his acute loyalty to Cardassia and belief that he was doing what he had to do for his people. His observation of some of the worst that sentient creatures - Cardassian and otherwise - are capable of in the murky underworld of covert operations has made him incredibly cynical but also fascinated with the Federation, particularly Julian Bashir, whose compassion and desire to help people is completely alien to him. Although he is incredibly dangerous if you get on his wrong side, his enforced "retirement" and consequent exposure to the Federation has allowed him to learn compassion and to lose his taste for the more unsavory aspects of his job description. His moral compass has definitely be pulled a certain way since he was exiled, leading him to act more like a Sociopathic Hero than a Retired Monster.
The show hints that he's been hiding dissident sympathies. When trapped between obeying the state (killing them) or letting them go free he acknowledges it's against his better judgement to oppose them and eventually lets them go free. It's not the last time he helps dissidents either much to the consternation of an old Obsidian Order colleague of his.
To Enabran Tain (who exiled him) he is clearly very upset over how things turned out between then (but then, we don't know the circumstances to know why).
When he was ordered to torture Odo, he's uncomfortable with the idea but carries it through and succeeds in torturing himself almost as much as he tortures Odo, begging Odo to give him even the smallest bit of information so he can have an excuse to stop the torture. Afterwards, he apologises to Odo and from it an Odd Friendship is born.
When he's commissioned by the Federation as a code-breaker in the fight against the Dominion (and therefore Cardassia), he suffers a claustrophobic breakdown which turns out to be as a result of him bottling an immense guilt over the role he's playing in the fight against Cardassians.
At the end of the show, he gives a speech observing how the decimation of Cardassia could be considered payback for the awful actions they've committed against other species during their military expansionist phase.
Also the man who did the exiling, Enabran Tain, Garak's superior and father and the man who ran the Obsidian Order for twenty years. Unlike Garak, Tain is a straight example of this trope, and completely unrepentant of his crimes and killing whoever might be a threat (while Garak seemed to be always looking for excuses to not kill someone, Tain seemed to be looking for excuses to kill). It's his missing the old days which prompts him to actually come out of retirement and forge an alliance with the Tal Shiar to strike at the Dominion preemptively. This doesn't end well.
Star Trek: Voyager: The Maquis crewmembers could also be considered a variant of this, as they were all former resistance fighters and terrorists who had done some unsavoury things to the Cardassians in the past. The most egregious example would be Lon Suder, who only joined up with the Maquis to satiate his need to kill.
Babylon 5: Deathwalker. She just wanted to get everyone else to do her dirty work.
Samson Gray, Sylar's father, on Heroes. A sadistic murderer who retired to live a quiet life as a taxidermist because he just got bored of killing. Until Sylar showed up with the power of healing, and thus immortality.
Sylar himself retook the identity of Gabriel Gray in the alternate future of "I Am Become Death", having gotten bored with acquiring power and all the pointless killing. Due to a Noodle Incident, he now lives in the former Bennet house dotingly raising his young son "Noah" and once again working as a watchmaker.
Bill Jarvis (formerly "The Hollow Creek Killer") from the Criminal Minds episode "Haunted".
In an episode of CSI: Crime Scene Investigation, a black janitor who befriended the murdered white supremacist student (who was trying to learn how to respect other races) turns out to be a leader in the Rwandan genocide. The student had found a picture of him in a book and was going to turn him in when the janitor murdered him
In Kings, Vesper Abbadon seems like a doddering old man, but there is a very good reason why he was called "the bloody King of Carmel." It's the same good reason why he's spent the last 30 years locked in a stone box with minimal human contact.
In the live-action version of The Tick, "The Terror" is an elderly old supervillain who was former buddies with Stalin. These days he's just a crazy old guy in a hospital whose antics amount to little more than throwing blood bags at Arthur. Considering Arthur's crappy level of fighting competence, that is actually a genuine challenge for him.
In The Sarah Connor Chronicles, Charles Fischer came back from a future in which he helped the machines to understand humans by torturing them to get inside their heads. He claims that he was sent back to the past as a reward for his services, and doesn't do anything particularly malicious. Subverted at the end when it's revealed that he accessed a computer system at his younger self's place of work in order to aid SkyNet.
Also to ensure his past self is in position to become him.
Duncan from Highlander: The Series is surprised that his friend and Cynical / Big Brother Mentor Methos is one of these. Back in The Bronze Age Methos joined with 3 other immortals to form a marauding pack that killed and burned their way through the world. (Inspiring the idea of The Four Horsemen along the way; Methos himself was Death). Although Methos never says that he's sorry, he is more guilty about his actions than most, calling those years his "angry adolescence" (this was after all 5000 years ago), and when Kronos, another member of the Horsemen tries to get group together again, Methos plays them and helps Duncan bring them down from the inside.
On Rookie Blue Jamie Brennan was a feared ganglang enforcer who was infamous for using power tools to torture his victims. After a small stint in jail on relatively petty charges, he got married and went straight. When his family is killed in a suspicious car accident he kidnaps and tortures an undercover police officer to find out if the police were covering up what really happened.
Grimm gives us several literal examples of this trope, monsters who have retired into quiet, suburban lives. The most prominent being Savage Wolf Monroe, who starts out as this but is eventually driven to a Heel-Face Turn.
Ex-cartel capo Hector "Tio" Salamanca on Breaking Bad, who despite being crippled and mute after a stroke has not to lost a bit of the sharpness - or ruthlessness - that characterized his younger days. (Said younger days are occasionally shown in flashback.)
How some of the older members of the mob end their careers in The Sopranos - the lucky ones. Then again, Uncle Junior's gradual descent into dementia, eventually rendering him a frail, senile husk of his former self condemned to spend the remainder of his life in a dank state-run facility unable to even recognize his family or recall his own accomplishments is one of the most depressing and haunting plotlines in the show.
Played for Black Comedy in an episode of Community where Troy and Abed befriend a fellow college student named Lukka, who teaches them how to succeed at a spectacularly violent war videogame. After a date with him, Britta finds out this is because he's an unrepentant Sociopathic Soldier and Balkan war criminal who quite giddily participated in genocide. Needless to say, Troy and Abed are pretty horrified when they find out about their new friend's past.
The demon lord Pale Night is an ancient being that many other demon lords claim is their mother (and some claim the entire current race of demons can trace their bloodline back to). Nowadays, she tends to stay in her palace, distancing herself from the mortals, the Blood War, and other demons... But, may the gods help anyone she catches trespassing on her property. Some she turns into souless husks whom she keeps as trophies (and guardians) while others she lets go, only to live with the horrors they've seen forever.
Another ancient demon who is now retired, but not by her choice, is the Queen of Chaos. In the mythic Age Before Ages eons ago, she ruled the obyrith, the race of demons that first populated the Abyss, and led them on a war of genocide against the Wind Dukes of Aaqa. She was such a monster, she murdered any obyrith who refused to join her forces. Eventually, however, her army was defeated by the Wind Dukes due to the creation of the Rod of Law (later the Rod of Seven Parts) her second in command and consort Miska the Wolf Spider was banished to Pandemonium, and the obyrith nearly driven to extinction as a result. Neither the Queen nor the obyrith ever recovered; since then, she has laired in the 14th layer of the Abyss, known as the Steaming Fen, licking her wounds, dreaming of freeing Miska and returning to glory.
The baernoloths are the creators of the yugoloth race (until the 4th edition, where the yugoloths were included among demons via retcon but long ago entrusted leadership of the race to the ultraloths and retreated to the farthest locales of the Grey Waste. The few encounters that mortals have with these ancient fiends have yielded reports of horrid and blasphemous experiments, but fortunately, the baernoloths don't seem to have the great power they are said to have once had.
Also, there are the Rabble of Devilkin, powerful unique devils who reside on the first layer of Hell. Technically, they are exiled, not retired, formerly being Dukes of Hell (or in the case of Moloch and Geryon, rulers of whole layers) who were stripped of their position for some reason, but spared death for other reasons. Most are content to simply stay in their lairs and keep to themselves, but a few have made vain attempts to regain their former positions, so much that in such cases, their names have been stripped of them to prevent mortals from summoning them. One notable Rabble is Armaros, a being who is believed to be the most powerful devil in existence and a wizard with godlike magical power. Only Asmodeus himself is allowed to visit him (which he does quite often, possibly for advice) and no-one else dares disturb his magical research.
A few ancient evil gods match this Trope; Legends say they were once powerful gods, but because this cosmology is one where Gods Need Prayer Badly, these gods suffered as their races became weaker and lost their influence on mortal worlds, becoming slothful and neglected due to the lack of worship. (This happens to non-evil gods too sometimes, but not as often, for some reason.) Examples include Ramenos, the frog-god of the bullywugs, Merrshaulk, the god of the yuan-ti (a race that challenged humans for dominance and lost), Laogzed, the deity worshipped by troglodytes (now little more than a giant lizard that other gods think of as a divine garbage disposal), and Gorellik, who used to be the patron deity of gnolls until that position was usurped by the demon lord Yeenoghu, causing him to wander the lower planes, seemingly with no purpose.
Fhjull Forked-Tongue, an unrepentant devil who was tricked into signing a deal with an angel that obligated him to do good. This got him thrown out of the hellish hierarchy, mutilated, and led to him hiding out in a place where NO ONE could find him just so that he doesn't have to actually abide by the contract (which roughly says "Give charity to anyone who asks.")
And of course, Ravel herself.
No... this world is full of thorns and Ravel has spent more than enough time a-picking them from her skin.
MadWorld states that Jack was a lesser form of this, being the former Grand Champion of the Deathwatch games, only quitting due to being tired of the games' reign of death. He does come out of retirement since he's sent to save the Mayor's daughter (until he learns she was never in any actual danger, and that in fact the Mayor and several of his friends set up the whole Distressed Damsel ploy for their own entertainment) and later to take down the games with the help of XIII.
Gig from Soul Nomad & the World Eaters. He once nearly destroyed the world. He wants a do-over, and this time, he'll spare nothing (except some hotpods, they're delicious). And he does not hide from the protagonists that this is his plan, or that taking advantage of his powers too much will release him, even though a little bit of deception would have him freed much quicker. And he's quite gung-ho about going off to kill Feinne, his former ally (though Feinne is far too powerful at this stage for them to succeed). And he'll chew you out for even suggesting he's not a bad guy. This gets played with a bit later when we find he was actually Brainwashed and Crazy and while he never reverts back to his original personality (in the Normal route at any rate) he does get enough Character Development to pull off a Heroic Sacrifice against the Big Bad. And then Redemption Equals Life.
Dragon Age: Origins has Flemeth, the Witch of the Wilds; infamous in legend for the countless atrocities she has committed throughout history. And the truth is even worse. She has allowed a demon to possess her, killed her second husband and everyone in his castle, and gleefully slaughters anyone who tries to hunt her down. And she makes a game of it, using her five-year-old daughter as bait. Not to mention she kidnaps, rapes, and murders men she finds in order to even have daughters, whom she raises just to use a ritual spell to take over their body so she can live forever. Don't be fooled when she offers help, she is NOT a nice old lady.
In Knights of the Old Republic II, Kreia. Once a Sith Master, she taught the two Sith Lords currently hunting the player. Throughout the game she insists she is Above Goodand Evil but her teachings of individualism and control inevitably lead toward the Dark Side. Eventually she comes out of retirement and becomes the final boss.
Mandalore counts, though he doesn't "mentor" you as much as the other one. He does share his cynical world view with you though and has no regrets about the violence he has partaken in.
A minor character from Mass Effect 2, a krogan referred to as "the Patriarch", fits. After being soundly defeated and crippled by current boss of Omega Aria T'loak, he can be found serving as her advisor in Afterlife, clearly broken and longing to return to his bloody glory days, when he was respected and feared. In a sidequest, Shepard has the option of coaxing him out of retirement in a couple of different ways.
Jericho from Fallout 3, to a T. He used to be a raider, and expresses some interest in taking up the life again, but spends the entire game just bumming around Megaton like every other NPC... at least until an evil Player Character convinces him to give it another shot. There's also the weapons dealers Flak and Shrapnel in Rivet City, a retired slaver and raider, respectively.
Level 50 characters with Evil or Very Evil Karma can take the "Ain't Like That Now" perk to restore it to Neutral levels and gain a bunch of bonuses. The name of the perk comes from a quote from the aforementioned William Munny.
John Marston, the main character of Red Dead Redemption, is considered by Edgar Ross to be this. Ross fails to see the irony or hypocrisy of the fact that Marston is trying to stop killing people and Ross is forcing him to keep killing people. And that he becomes this trope as well (From a Certain Point of View).
The vampire Vorador spends most of the Legacy of Kain series as a Retired Monster, having given up on the mortal world after the murder of Janos Audron- though not before killing off most of the Circle of Nine in revenge. He's clearly still as hedonistic and depraved as ever, living in a luxurious mansion (complete with a torture chamber), surrounding himself with brides, drinking the blood of human captives from golden goblets; nonetheless, he advises Kain to avoid meddling in the affairs of mortals. If only he'd listened...
Certainly Travis in No More Heroes 2: Desperate Struggle. He doesn't even remember the first assassin he killed when his brother comes for revenge. Well, he is this to a point...he most likely still hasn't gotten past how he dishonored Holly Summers by not killing her in battle when she wanted such a fate. Otherwise, he doesn't care to get back into the games until Bishop is killed and Sylvia "convinces" him, perfectly fine with his pathetic lifestyle. It's mainly because killing has become boring to him after killing the best of the best. He does regret killing Charlie's cheerleaders but that and Holly seem to be is only two regrets.
Paarthurnax in The Elder Scrolls V: Skyrim, leader of the Greybeards and former right-hand man of Alduin, who turned against the rest of Dragonkind and sided with Humanity during the Dragon Wars, teaching the Ancient Nords the art of the Thu'um. When questioned about his former crimes and his reformation by the Dragonborn, Paarthurnax admits that he can never truly reform and even after several millennia, he still has the innate urge to conquer and destroy as all Dragons do, but has merely learned to suppress it with daily meditation and intense self-control.
Michael Townley in Grand Theft Auto V, who was one of the most prolific bank robbers in the Midwest. He managed to cut a deal with Agent Dave Norton of the FIB, which allowed him to retire to the West Coast under Witness Protection and a good stipend, under the name "De Santa." Eventually, the plot starts when circumstances force Michael back into his old profession after nine years.
Dan's mother was a monster, but why she apparently stopped and how she feels about that time has not been explored. And it seems she might not be so "retired" considering she sent a hit team after Abel, considered her stepdaughter acceptable collateral damage, and is plotting the genocide of the dragon species.
Mr Garrott (the eldest), from Wiglaf and Mordred. The patriarch of a family that employs people who could be supervillains in their own right as household staff. Just how terrifying he can be is demonstrated when, while he expresses his displeasure with several members of the household staff, it cuts to two characters who were watching him discipline members of the staff, One asking, "Is it over yet!? I'm not supposed to be seeing this stuff live! I read about it later! He's supposed to be retired!" Meanwhile, the other person watching comments on how, asides from the gray hair, Mr Garrot has not changed at all since retiring thirty years ago.
Succubus matriarch Blacksky from The Return who believes world domination is just too boring these days.
In the Eridanus Galaxy online web game Imperium Nova, the Vampire Count Sergio Von Carstein announced his retirement at the age of 74 after a number of evil acts, including brutally suppressing several human and vampire rebellions, engineering a plague so he could reanimated the corpses to work his farms, attempting to brutally murder several fellow nobles, hooking up hundreds of thousands of humans to blood extraction machines, creating a gigantic zombie horde out of a military cemetery, and a career in organized crime.
Rich from the MSF High Forum, pretty much qualifies. There's a reason Mel'lon does not like him.
Not all the teachers and staff at Whateley Academy in the Whateley Universe are retired superheroes. The story "Test Tubes Babies" ultimately reveals that one of the teachers we know is a retired supervillain and mass murderer. In "Mimeographic" we find out that the first house father of the school was a retired evil wizard.
Stewie Griffin from Family Guy is one, best seen in the episode "Stu and Stewie's Excellent Adventure" (from "The Movie Stewie Griffin: The Untold Story"). As an evident example of the early seasons, he was a psychopathic little brat who enjoyed using violence at any moment, at point that even the two-part episode "Stewie Kills Lois and Lois Kills Stewie" showed how monstrous he was able to be, not to mention that in the real canon has killed several people, even kids. However, the episode "Stu and Stewie's Excellent Adventure" showed us that his self-future is one of these. He is not violent and all his plans for world domination were scrapped by himself.
Also there's the fact that in every new season, it seems to become increasingly sympathetic. It may seem strange that even now can be considered an Anti-Hero, and less evil than Carter.
Eric Cartman from South Park is a variation and subversion of this trope, since he is not old. While several episodes showed his monstrous behavior, extremely sadistic and generally no regrets for his actions, the episode "The Death of Eric Cartman" seems to establish him as a self-redemption. Also, recent episodes of season 16 seems to show that he has been softening in his villainy. The episode "Jewpacabra" is another candidate. But do not question that Cartman did many atrocities in the past, including the infamous act of "Scott Tenorman Most Die", murder and attempted genocide in "Coon & Friends"
Also, he's shown to grow up to be more or less a stable adult, as seen on "My Future Self and Me" (at least until Cartman binges on doughnuts and turns his slim future self into a fat wreck).
In one episode of Batman Beyond, Bane was revealed to have become a crippled old man thanks to his constant abuse of venom.
The title character of the Samurai Jack episode "The Tale of X9" fits the Trope, being a former robotic assassin and cold-blooded killer. You couldn't help but feel sorry for him though, seeing as he retired out of his love for a puppy (and was only capable of feeling love due to an Emotion Chip) and came out of retirement because said puppy had been kidnapped. Despite his past deeds, the situation made him a very sympathetic figure among fans, who regarded his death at the end one of the saddest moments of the whole series.