A Walk Through Hell: Shaw suffers a major case of this in the penultimate issue, when she learns that her boss and mentor Agent Driscoll had previously uncovered the conspiracy to protect Carnahan; not only did she sit on the information, but she also manipulated Shaw into taking the law into her own hands and killing Carnahan, thereby setting off the events of the story.
In Chuck Dixon's Avalon, King Ace gets to work with Big Simba and his crew, thinking they'll be using their powers to rid the streets of dangerous criminals. He soon learns that Simba is just an ordinary, unpowered body-builder and, far worse, the team is a glorified hit squad.
In Death of the Family, the Batfamily is unhappy with Batman for keeping at least one secret from them. In fact, Joker could be counting on this trope to sabotage his enemies. That was his motive, to figuratively cause the death of the Bat-family by breaking their trust in each other.
This is how Batman finally defeats Deacon Blackfire in Batman: The Cult — he realizes Blackfire wants to die at Batman's hands so he can become a martyr, thus Batman attacks him to show his followers that he isn't immortal, but just a man. His drugged and broken followers are so enraged by the weakness that they finish the job.
Before becoming Robin himself Tim Drake was in awe of Dick Grayson, Jason Todd and Bruce. The one who should have had the hardest time failing to live up to Tim's expectations was the deceased Jason who instead came back from the dead and turned on the Batfamily, became a serial killer, and repeatedly attacked Tim because he felt the lesson of his death wasn't learned by the superhero community and because he was furious at being "replaced".
Bruce preventing Stephanie Brown from visiting Tim while she was Robin, hiring Steph and then unceremoniously firing her in an attempt to manipulate Tim back into the role, and preventing anyone from even telling Tim that she was missing while she was being tortured to death permanently altered the lens through which Tim views Bruce in a way little else could.
Tim Drake: "During my visit it took every bit of discipline I could conjure to keep from asking Bruce that one terrible question I'm stone cold certain our relationship can't survive. 'What happened in those last moments between you and Stephanie, and why did you keep me from being there?'"
In Bruce Wayne: Fugitive, Deadshot takes a contract to kill his mentor David Cain from Lex Luthor, and is disgusted by how much Cain, his former idol, has fallen apart.
Eddie Bloomberg aka Kid Devil idolized Blue Devil and wanted to be a hero just like him. When he made the Deal with the Devil that turned him into the superpowered Kid Devil, said Devil Neron stated that Eddie's soul would belong to him if his trust in Blue Devil was ever broken. After the deal was made, Neron told Eddie that Blue Devil had made a deal with Neron for movie stardom that accidentally (on Blue Devil's part) claimed the life of Eddie's aunt Marla. When Eddie confronted Blue Devil about it and Blue Devil confirmed it, Eddie resigned himself to becoming Neron's slave because he would never trust Blue Devil again.
The Chief (Niles Caulder) of the Doom Patrol. Turns out that, believing that greatness comes from overcoming tragedy, he engineered the accidents that gave the original Doom Patrol their powers. He eventually tried to take his plan global before he was finally stopped. He's supposedly reformed since then, but let's hope the Patrol is smart enough to keep an eye on him. Half of them are just as nuts as he is, at least one fell in with a better crew, and all of them follow the Manipulative Bastard even though they know full well he's a Manipulative Bastard. At least other, non-Doom Patrol superheroes are always visibly put out of sorts when Caulder's around.
Green Lantern: Sinestro was once considered to be the greatest Green Lantern to have ever existed and was a mentor to Hal Jordan. But eventually, it came out that Sinestro was a tyrant on his homeworld and was exiled, becoming an enemy to the Corps (especially Hal). This trope is invoked a lot when they go head to head, mixed with We Used to Be Friends (because Sinestro has had exactly two friends in his life; Abin Sur, his mentor, and Hal Jordan, his greatest student), with Hal sometimes genuinely pleading with Sinestro to try and be better, and Sinestro once saying sadly that the tragedy of it all is not that they were once friends, it's that they'll always be friends.
Infinite Crisis: Superboy-Prime gave up his home, family and friends to save the Multiverse during the Crisis. He then was imprisoned in a pocket dimension to make sure he survived the reconstruction of creation. How is he repaid? He has to watch his heroes get corrupted for years. How does he react? Not well.
Subverted in their first appearance. After Superboy fails his three initiation tests, the Legionnaires laugh and mock his reputation as the greatest hero ever. Before Superboy leaves, though, they confess they were pranking him, and he has more than lived up to their expectations.
During the 1990s reboot, Livewire constantly warns sister Spark of misusing their lightning powers. It comes out that Livewire is worried that using them too much will drive them insane as it did their older brother Mekt, who became the criminal Lightning Lord. Even when Mekt kills a cop before him, Livewire is begging him to stop so they can get him help. In a fight, Sparks is astounded by Livewire going "the lightning drove him mad" and snaps that everyone else in the family already saw what Garth didn't: That Mekt was always this twisted criminal and the lightning did nothing to change him. It takes having his arm blown off and Sparks nearly killed for Garth to accept his brother was never this great person he thought he was.
Sparks: That's what you think? That our powers corrupted him? Garth, you looked up to him too much! You didn't see what the rest of us saw! That Mekt was always a—- Mekt: I was always a what? Sparks: A misanthrophic, self-obsessed, sociopathic, parasitic and, incidentally, boring bag of slime!
The Flash: Subverted in The Return of Barry Allen. Wally West is sent into a Heroic BSoD when his mentor and hero Barry leaves him to die out of jealousy, but he then discovers that "Barry" is actually an amnesiac Reverse-Flash who simply believes he's Barry.
Shade, the Changing Man: Loma Shade, the titular character of the Young Animal imprint's Shade, the Changing Girl, is initially a fan of Rac Shade and made her own journey to Earth using the Madness Vest to be like her idol, but ends up condemning Rac Shade after seeing what a (literally) heartless monster he's become in the Shade, the Changing Woman miniseries.
How Luthor Met Superboy: In the Pre-Crisis era, young Lex Luthor was a total Superboy fanboy until his lab got burned down, and he convinced himself that Superboy started the fire out of jealousy to destroy his great discovery.
Post-1986 /Lex Luthor was gone through two major cycles of this: first as a Corrupt Corporate Executive and second as President Evil. In the former case, Lex was a hero to the city who employed half of Metropolis. He kept his criminal activities hidden until clone degeneration affected his second body, triggering a rampage. The second time, Lex rose to even greater heights as the rebuilder of Metropolis and Gotham (in the public's eyes), who won the presidency as the darkhorse third party candidate and helped save the world from Imperiex, only to go crazy from Kryptonite injections as he prepared to use all his resources and goodwill to take down Superman once and for all.
In Elseworld's Finest: Supergirl & Batgirl, Supergirl befriended Lex Luthor shortly after arriving on Earth. She regarded him as a good friend and a surrogate father and mentor, and she thought that he was a very, very good man who loved helping people. Then she discovered that he was a bigoted, selfish, egomaniac, uncaring, murderous, manipulative bastard.
Death & the Family: Supergirl feels so hurt by Lana Lang keeping important secrets from her that decides to leave her mother figure for a while. Subverted in later storyline Bizarrogirl, when Kara considers she was too harsh and apologizes to Lana.
Supergirl:"When you started...mentoring me, the whole goal of it was to teach me more about being human. We built a trust. For a year, I told you everything. You knew all the stuff that was wrong with my life. [...]But you lied to me, Lana, that entire year. You didn't trust me, and people in that hospital died because of it. You died because of it. I saw you die. Because you were scared to tell me something was wrong." Lana Lang:"Kara, I—" Supergirl:"Let me finish. Insect Queen wanted me to think she was the reason you put so much faith in me. That she was why we'd built a trust. Even if that's not true, our trust was still one-sided. And if I can't put belief in our trust, what good is this relationship?"
The Leper from Krypton: Lexor was a planet where Lex Luthor was considered a hero because he used his scientific genius to help their inhabitants to build an advanced civilization; and they were so grateful that they renamed the planet after their benefactor. However, when they find out he engineered a biological weapon in order to murder Superman, the Lexorians are so enraged that they throw Lex's statues down, burn his books and tear his machines down.
Wonder WomanVol 1: When the Earth One version of Diana learns that her mother has modified her memories to try and control her relationship with Steve Trevor — mostly erasing the fact that he'd died and been brought back twice from Diana's mind — it breaks her trust of her mother permanently. This makes Diana's relationship with Hippolyta more distant and strained from then on, with her not speaking with her mother for months at a time.
Laika: Yelena believes her superior, Korolev, is kind at first, and is moved by his statement that the Soviets are proud of their space dogs and their "big Russian hearts." Later, after a rocket crash that killed two of the dogs, Gazenko bluntly tells her that Korolev will stop at nothing to achieve his goals and does not prioritize the safety of humans, let alone "dumb mutts."
All-New Ultimates: O'Reilly used to be grateful of Scourge trying to help the police on his own. He was detained and interrogated, and it turns out that he was a racist maniac.
Black Panther: Despite utterly loathing T'challa, Erik Killmonger actually idolized The Avengers as a young man. During the brief period where he became the new Black Panther after defeating T'Challa, he petitioned to gain membership in the group, and even teamed up with them during a battle involving Deadpool. The battle in question caused him to lose his respect for the Avengers, as he felt the fact that they abide by rules imposed on them by the government made them a pack of spineless cowards.
Around the time Spider-Man finally officially joined The Avengers, Tony Stark became something of a mentor to Peter. The two gravitated to each other, being the only members of the team at the time who were scientifically minded, and after the infamous The Other storyline, Tony even designed Peter a new Spider-Man armor much like his own. This "mentorship" culminated during Civil War (2006) when Tony essentially made Peter his Number Two on the Pro Registration side. Eventually, their friendship completely dissolved when Peter learned the extremes Tony was resorting to during the event.
The entire run of Superior Spider Man is this, watching various heroes and villains just being utterly gobsmacked by this much more vicious Spidey, not knowing that Dr. Octopus had taken over Peter's body and has no idea how Spidey truly operates.
During Spider-Geddon, the Spider-Man from the 2018 Playstation 4 game starts looking up to the Superior Spider-Man because he felt that he was what his world's Otto Octavius could have been had he not fallen. However, when he asks Miles Morales more about him, that all changes, especially after Otto willingly gave the Ben Reilly Scarlet Spider to the Inheritors.
In the crossover Spider-Man and Batman: Disordered Minds, we learn that Carnage is a massive fanboy towards The Joker. However, that all goes down the pot when Carnage grows tired of Joker's theatrics and the Joker just absolutely hates Carnage's idea of randomly murdering people without any form of comedy.
The Thunderbolts were originally the Masters of Evil disguised as heroes to gain public trust. Needless to say, the public was quite rocked when their true identities were revealed. Teenage member Jolt (who hadn't known about the scam) is especially jarred to find the folks she'd called friends were nothing but super-villains.
Sunspot from New Mutants used to idolise his father, and was so close to him that they were practically best friends. Then he learnt that his father had thrown his lot in with the villainous Hellfire Club, with one of his first actions being to send out a hit on Sunspot's mother. He subsequently disowns his father, and his concern that he'll grow up to be like him becomes an ongoing issue.
Xavier is Cyclops' broken pedestal. Since learning of Xavier's various misuses of his telepathic powers to rewrite Scott's memories and cover up old shame, Cyclops has had great difficulty dealing with Xavier's betrayal. It eventually culminated with Cyclops financially seizing control of the Xavier Institute and kicking Professor Xavier out of his own home.
This goes into overdrive in Inferno (2021) as the Quiet Council learns the scope of Xavier, Magneto and the actually-alive Moria MacTaggert's plans with creating Krakoa. The Council was already in a bad state as it was, being an alliance of X-Men and Hellfire Club members, but this made it worse.
In Ms. Tree, Dan Green worshipped his older brother Victor who went MIA during The Vietnam War. Dan ultimately undertook a mission to Vietnam attempting to locate his brother's body, only to discover that Victor was still alive and living as a crimelord.
Once & Future: As much as Bridgette drove him crazy at times, Duncan thought the world of his gran as his only parental figure growing up. But the more he learns about his family's history and the monster hunting business, the more disillusioned he becomes with Bridgette for lying to him and using him.
Duncan: I don't think I can do this. Bridgette: You're in the family trade, now. You have to. Duncan: No, I can do that. I don't think I can do us.
The Powerpuff Girls are fans of cartoon hero Tess Turbine (DC Issue #38, "To Be Or Not TV"). They're geeked when they hear that Tess is appearing in person in Townsville, but when a monster invades Townsville and takes Tess (actually an actress hired to play Tess) captive and she can't defend or help herself like in the cartoon, the girls renounce her. The Professor has to persuade the girls to put their hurt feelings aside and rescue Tess like the superheroes they are.
Subverted in Preacher: Jesse Custer's father figure (past the age of 5) who taught him how to fight, shoot, and grow up was Jody, the Small-Town Tyrant who ruined his life and killed his father. But he knew this the entire time, and eventually paid him back for it by choking him to death with his bare hands instead of using the "Word of God". His last words to Jessie before his murder at Jesse's hands "Proud o' you boy".
Sonic the Hedgehog (IDW): Dr. Starline has made a career of studying Dr. Eggman, and is initially ecstatic when Eggman enlists him into his ranks. Over time, however, Starline begins to break out of his villain-worship of the portly megalomaniac, particularly after he unleashes the MetalVirus after performing the bare minimum of tests and dismissing his concerns, reasoning that they can fix any bugs as they pop up. He eventually confides in Orbot that he always thought that Eggman always lost because Sonic was just that good, but is now starting to realize it's because Eggman refuses to plan for or adapt to the long-term; he's dismayed to discover from Orbot that it's usually either that, or being blinded by his hatred of Sonic and self-destructing. He finally reaches his breaking point in issue 23, finally sick of Eggman's utter incompetence with the Metal Virus and careless disregard towards any form of safety precautions. He comes to realize that even Neo Metal Sonic's earlier failures were brought on by the robot having absorbed Eggman's bio-data, leading to the exact same failures in the exact same places. Starline concludes that he idolized Eggman's legend alone, and that the man himself simply didn't measure up to it.
Starline: I got lost in his pageantry—in his showmanship. I was inspired by Eggman's legend. The man simply doesn't measure up.
In Star WarsLegacy, Imperial Knight Antares Draco looked up to his master Eshkar Niin as a wise teacher and still values the lessons he taught, but his faith in his master was shattered when Niin deserted the Order and murdered the Empress for seemingly no reason, forcing Draco to kill his renegade master in a duel to the death. Draco is understandably shaken when he later learns that Niin not only survived their duel, but has since become a Sith Inquisitor under the name Darth Havok.
Sunny Series: Sunny looked up to and cared deeply for her older brother Dale—which is why she's so upset that his substance abuse resulted in him treating her poorly, expecting her to keep secrets, and even hitting her on accident in a drunken rage when she tried to stop a fight between him and their father on the Fourth of July. She does not get over his actions easily, and Dale's resentful after being sent to Military School to stop the problem. Sunny often wishes that he could just get better instantly—she says she misses him when he's gone, but doesn't miss what he's like when he's there given his actions. She and her mother both have a good cry about it in his room when she admits this. Things do improve; Dale finally starts to adapt to what military school is for him, becomes a Recovered Addict, and later joins the Navy.
Suzy, a British girls' comic from the 1980s, once featured a photo story in which the main character wins the chance to meet her favourite (fictional) pop star, only to find that he is a jerkass who's only interested in making money. The story ends with her tearing up a poster of the pop star in question, having decided she "never wants to see or hear him again."
Early on, Orion Pax — the future Optimus Prime - looked up to Megatron as an inspiring figure, a champion of the downtrodden against the corrupt Senate that Pax reluctantly served. Then Megatron started succumbing to He Who Fights Monsters.
Megatron got it from the other side after his surrender and Heel–Face Turn during Dark Cybertron, becoming the number one target of his own protege, Tarn of the Decepticon Justice Division. Turns out that organising a kill-squad to brutally murder defectors can be a problem when you become one.
Optimus himself spends a distressing amount of time discovering just how unpleasant the lineage of Primes were. At one point Rodimus has to give him a pep-talk where he tells Optimus that it doesn't matter if every other Prime was ten tons of bastard on a five-ton chassis, what's important is that Optimus can use that false legacy to inspire people to greatness.
In a turnabout, Optimus becomes increasingly ruthless and manipulative later in the series, to the point where after a while most of the Autobots are skeptical of him and his closest ally is Soundwave of all people.
Ironfist was initially the single biggest Wreckers Fanboy in the universe. Then he got to accompany them on a mission and learned that far from noble heroes sacrificing themselves in heroic adventures, the Wreckers are an Anti-Hero suicide squad who do Dirty Business...and that's on a good day. In particular, he's appalled by the truth about Squadron X, the Wreckers' Evil Counterpart: instead of capturing them under legitimate circumstances and killing them as they tried to escape, the Wreckers ambushed them in an illegal operation on neutral territory, after ignoring orders related to several battles - including the biggest one in Cybertronian history - to continue pursuing them, won when Impactor fired through a protesting Springer, and then Impactor murdered them in cold blood after being told he had to let them go, while everyone but Springer stood around and looked sad but did nothing. It probably didn't help that he'd devoted a lot of time to writing the "Wreckers Declassified" datalogs that had ended up whitewashing these brutal actions and occasional war crimes into outright propaganda.
Space Usagi: Usagi's mentor, who happens to be his slain lord's brother and the current lord's uncle, is actually the one who hired the ninjas that killed his lord in the first place. He's also kidnapped his nephew to mind probe the location of the royal treasury. In a separate story, the person who killed Usagi's own father was someone that both of them respected and admired. Both stories lead to an inevitable showdown.
