Writer Alan Grant was told straight up that this would be the fate of his Batman character Anarky, who he'd set out to establish as The Joker's son. Originally conceived as a plan by Anarky illustrator, Norm Breyfogle, to create tension in the character, Grant approached Dennis O'Neil, who had editorial oversight on all Batman books at the time. O'Neil was dead-set against the idea, but gave permission on the express condition that it wouldn't be true, and would be revealed as false months later, whether by Grant or by another writer. As the series was canceled before this could happen, it remains unaddressed. With the establishment of the New 52, it no longer exists as a hanging storyline at all.
The non-canon Batman miniseries Batman: White Knight by Sean Murphy is generally a pretty even-handed and nuanced attempt to grapple with the "is Batman actually as insane and vicious as his villains?"/"does Batman's presence inspire villains to get freakier?" questions in Batman fandom. However, its portrayal of Harley Quinn strays into this territory, as it criticises post-Flashpoint depictions of Harley by splitting her into two completely-different characters — the original Harleen Quinzel, who wears her modest classic costume, never did anything truly evil, and just wants to make the Joker happy and saner, and the second Harley, actually a woman called Marian Drew, who is an Ax-Crazy killer with a Stripperific costume, is worse than the Joker ever was, and becomes the Big Bad of the comic. Some fans viewed this as significantly whitewashing the earlier canon Harley and ignoring the evil stuff that she did pre-Flashpoint. There was further controversy when he wrote a Harley Quinn mini-series set in this continuity, which depicted the second, evil, Harley as dating Poison Ivy, and had the "real" Harley express disgust towards homosexuality, when the Homoerotic Subtext between Harley and Ivy had begun as early as her original portrayal in Batman: The Animated Series.
In an issue of Outsiders, Judd Winick had Arsenal completely out of nowhere make out with Huntress and then tell Nightwing that he'd had sex with her. Gail Simone responded by writing a scene in Birds of Prey where Huntress admitted to sleeping with Arsenal, but then followed up by saying he wasn't very good in bed.
Speaking of Arsenal, the 90s Teen Titans series had a story where the villain Haze gifted him with the Red Arrow costume from Kingdom Come after entering his mind and realizing that Roy's deepest desire was to be Green Arrow's successor. Devin Grayson was not a fan of this development, so her later Arsenal mini-series had the new suit get destroyed during a fight. She then took it a step further by having Roy admit that he never really wanted to be Red Arrow or follow in Green Arrow's footsteps, and was content to continue being his own man. In reality, the mental hangup that Haze had witnessed was actually Roy's bitterness over not even having been approached to carry on his mentor's legacy, which added to his own sense of worthlessness. Coincidentally, in a Brad Melzter's opening Justice League of America arc, Roy did become Red Arrow, after Green Arrow gave Green Lantern the costume to give to Roy, because Ollie figured Roy wouldn't accept it coming from him.
In the Spanish arc of Bombshells United, Jasón deciding to die again due to the side-effects of Lazarus Pit resurrection has obvious subtext relating to Marguerite Bennett's views about the character in the mainstream DC universe.
In one issue of Captain Atom, writer Greg Weisman attempted to explain multiple personifications of death in DCU, as aspects of death - the Black Racer represented Death as an inevitability, Nekron represented death as the ultimate enemy, and Death of the Endless represented "the peaceful death that comes to the righteous". This annoyed the creator of the Endless, Neil Gaiman, who responded in interviews and a scene in which Death declared that she represents the death of everything, including the Universe itself, without any single exception.
John Byrne's revival fused this with outright Canon Discontinuity and Cosmic Retcon by rebooting the canon to focus on a revamped version of the original roster (The Chief, Robotman, Negative Man and Elasti-Girl), adding new characters Nudge, Grunt and Vortex as additional recruits and ignoring the history of all the comic's previous versions, in particular Grant Morrison's beloved tenure, which had itself been mildly fired upon during Rachel Pollack's run for Vertigo. This was rectified by Geoff Johns and Keith Giffen making everything from past writers canonical... Which, considering the nature of the book even before Morrison's entrance, fit just fine.
Paul Kupperberg's first revival of the Doom Patrol established that Larry Trainor (Negative Man) had somehow managed to survive the explosion that killed the team at the end of the series. However, Keith Giffen's run retconned things so Trainor actually did die in the explosion, and was covertly cloned by the Chief. Giffen also revealed that the "Negative spirit" is actually Larry's disembodied soul and that he had inhabited Valentina Vostok (Negative Woman) for some time, causing him to take on some of her memories. Furthermore, Giffen revealed that Larry's current body is that of a brain-dead man who was genetically altered to resemble him.
Valentina herself turned up towards the end of the series Checkmate, as the new White Queen and without her powers. However, a throwaway spread in Final Crisis #4 depicted a dead Negative Woman. In Resist, the civilian Vostok is then shown again, under Darkseid's control. Keith Giffen decided to count the appearance of the dead Negative Woman as canonical, ignoring Vostok's later appearance, and used her in the "Blackest Night" tie-in to Doom Patrol.
During John Arcudi's run on the series, transgender heroine Coagula was killed by teenager Dorothy Spinner (who was then killed by Cliff), solely because they were two of the last remaining members of the nineties team and Arcudi wanted an excuse for the nineties team to disband so that his own team of unrelated characters could take over. They remained conspicuously dead for nearly two decades, even as other dead DP members like Elasti-Girl and Negative Man were given resurrections. Genderfluid writer Jude Deluca hated this story, and hated that the two characters remained dead even after several line-wide continuity reboots, and so when they got a chance to co-write a story for DC Pride 2022, they had Kate and Dorothy show up in a crowd scene, making it canon that they exist in the modern Prime Earth. However, the 2023 miniseries Unstoppable Doom Patrol by Dennis Culver disregards this and still establishes Dorothy Spinner and Kate Godwin to be deceased.
Keith Giffen's run, aside from the aforementioned changes to Negative Man's character, had Mento written out after Elasti-Girl breaks up with him over the revelation that he was an abusive pervert who used his mental abilities to make Rita submit to his wishes. Gerard Way's run established that Larry Trainor's Negative Spirit was indeed a separate being (and given the name Keeg Bovo), while the Weight of the Worlds miniseries disregards Mento's abusive behavior by having an incarnation of Mento from a Bad Future appear to try and help the team prevent his future from transpiring, with Rita showing no signs of hostility towards Steve and behaving more like she's seen a disappeared loved one for the first time in ages rather than crossing paths with an abusive ex she fiercely severed ties with.
The Flash (2016) and The Flash (Infinite Frontier) both take shots at the infamous Heroes in Crisis event. Said event turned Wally West into a murderer after he had a mental breakdown that resulted in him losing control of the Speed Force. This caused an explosion that killed everyone at the superhero therapy centre Sanctuary, which Wally proceeded to cover up by gaslighting Harley Quinn and Booster Gold and desecrating the bodies of the deceased. Both the 2016 run and Infinite Frontier (which were released in extremely close proximity to each other) in conjunction basically remove Wally's fault in pretty much everything:
The 2016 run's final arc, "Finish Line", has the reveal that Eobard Thawne possesses a Negative Speed Force power that allows him to hypnotise people and force them to do things, and he uses this at superspeed so nobody knows it happened. He gloats that he's the one who made Wally do all the twisted things he did to cover up the incident.
The Infinite Frontier run's first arc, "Blink of an Eye", reveals that the explosion itself wasn't even Wally's fault. Rather, it was the fault of the Speed Force trying to expel someone tampering with it from within: Wally's enemy Savitar. The DC Infinite Frontier one-shot itself also brought back Roy Harper, while the era's last Flash arc, One-Minute War, undoes all the other deaths by saying Gold Beetle replaced them with clones at the time of their deaths, something that fans suggested could've been done when Heroes in Crisis was first published, since it was used as a solution for Wally's "death" in the same story.
Harley Quinn: The controversy over Harley's New 52 costume redesign (which included some writers who preferred the old costume openly mocking the new one in their own comics) is alluded to in #21, where Harley has a run-in with a character impersonator on Hollywood Boulevard who is wearing her old costume. Harley says that she only wears that costume on "special occasions", and when the impersonator accuses her of making a complete mess of being Harley, Harley pistol-whips her.
Geoff Johns is generally thought of as one of the best DC Comics writers when it comes to sticking to continuity, but almost every book he's been involved in has undergone some degree of change to his character or just plain retconning.
Reversed Jerry Ordway's characterisation of Black Adam, so that instead of a demon-worshipper in the body of a contrite murderer, he's a Namor-type Knight Templar in the body of an unrepentant killer. (Although this change at least didn't generate too much vitriol from the fans in the way some other examples on this page have, and some of the stories it generated - such as the Black Reign arc in JSA - are quite popular)
In the letter column from an issue of the Superboy (1994) series – starring Kon-El, who at the time was established as a human clone with implanted Kryptonian powers – a certain young "Geoffrey Johns" suggested that Kon was cloned from Lex Luthor's DNA. Editorial responded in no uncertain terms that this wasn't the case, as Kon's DNA donor was the director of Project Cadmus. Fast-forward to 2003, when Geoff Johns became the writer of the relaunched Teen Titans series with Kon-El as a member of the team, he immediately retconned Kon-El to be a Half-Human Hybrid clone of Superman and Lex Luthor.
Claimed that every single appearance of the Post-CrisisBrainiac wasn't really him at all, but was a Brainiac-probe in Superman: Brainiac. Even Milton Fine, who was taken over by nanoprobes, rather than psychically possessed by Brainiac's intelligence.
In that same series, Johns retconned Supergirl's previous backstory in favor of one more in line with her Silver Age origin, minus the campiest parts and keeping Supergirl as chronologically older than Superman but in stasis for years. It wasn't a bad thing, though, since Post-Crisis Kara Zor-El's origins had been retconned severaltimes previously, and Johns' updated origin stuck around because unlike the former backstories it worked.
Johns also retconned the 1992 storyline where Toyman murdered Catherine Grant's son by explaining Adam Grant was murdered by an out-of-control duplicate.
After Hawkman was rendered "radioactive" in the wake of Zero Hour: Crisis in Time!, Johns resurrected the Golden Age Hawkman while leaving the Silver Age alien one in limbo. While this version worked out well, Jim Starlin (for reasons known only to him) decided to retcon the Johns-written character, making the Hawkman who was part of the JSA be the alien Hawkman. It's gotten so confusing, Hawkman is now somehow both the Gold and Silver Age Hawks at the same time.
Tangentially related to the Hawkman snarl is the volley handling of his son, Hector Hall, and Hector's surrounding characters once he was reincarnated as the new Doctor Fate. What makes this particularly headache inducing is that Johns was volleying against himself, as if he couldn't decide which direction he wanted to take the character. As just one example of this, first all the prior Fates live in the amulet, then they're just hallucinations conjured up by Nabu, then, no, they're actually real again, then they all disappear again.
Johns also undid Green Lantern Hal Jordan's character derailment, who had been turned into an evil supervillain named Parallax and killed off in a massively unpopular story, by explaining that "Parallax" was actually a fear-based mental parasite who was corrupting Hal. He also took the opportunity to blame the parasite for Hal's greying hair, claiming it had prematurely aged him, and restored Hal's hair to brown.
Geoff also did a Take That! against Brad Meltzer and his Identity Crisis (2004) series, which, at one point, had a series of offhand scenes showing some B and D-list heroes Jack Bauer interrogating the Rogues, enemies of The Flash, one of the most powerful heroes on the planet, whom Johns was writing at the time. Cue next month's Flash showing those exact same scenes playing out to the end, with the Rogues soundly thrashing the heroes and going on their way.
Duela Dent, the so-called "Joker's Daughter", was a heroine created by Bob Rozakis. The character introduced herself with a wacky origin as the daughter of the Joker but, after pretending to be the daughter of several other villains, admitted that she was actually Harvey Dent's daughter. However, since he established that she was born after he became Two-Face (which would mean she should've been a child at best and not a teenager), it created a plothole that annoyed other creators and confused fans. Marv Wolfman addressed this in Tales of The Teen Titans #50, where Dick directly confronts her on this discrepancy, but she escapes before he can learn the truth. Post-Crisis, it was suggested that she might not be lying after all, and is actually time-displaced. At least until the events of Countdown to Final Crisis, where Duela Dent's origin was retconned as her not only being multiversally-displaced, but also the offspring of the Jokester, a heroic version of the Joker from Earth-3; a tie-in comic would soon follow, insisting that she was still a Dent by way of her mother being the Earth-3 version of Two-Face, seemingly solving the mystery for good. Except some writers still weren't happy with this, as come the New 52 reboot that followed Flashpoint, not only was she no longer a hero, but she was now completely unrelated to any other character in the DC multiverse (villain or otherwise), instead being a psychotic young woman with an obsession with the Joker to the point of injecting herself with the man's blood.
The villain decay was started by his own creator. Many fans forget, after all the build-up, Prometheus was defeated in his first caper by being whipped in the 'nads by a disguised Catwoman. And it was all downhill from there.
Cry For Justice had a controversial scene implying that Green Lantern Hal Jordan had at some point had a drunken threesome with Huntress and Lady Blackhawk of Birds of Prey fame. Gail Simone wasn't very happy about that and revealed that what that scene was really referring to was that the girls had once seen Hal pass out drunk at a pilot convention.
V4 Legion of Super-Heroes, having been written by fans, has a lot of this. For instance, fan speculation had had it that Element Lad is gay, but the previous writers gave him a girlfriend. When the fans got to write the book, his girlfriend was retconned into a man taking sex-change drugs. (Weirdly, they wrote Element Lad as unaware of this, so its relevance to his own sexuality is... unclear.)
Maxwell Lord. Back in Justice League International, he was a Lovable Rogue who genuinely believed in his team, even if he'd only formed them because an evil computer forced him to. Then in Countdown To Infinite Crisis, it turns out he's a ranting metahuman-hater who set his League up to fail. Then, in Booster Gold, Geoff Johns says "Remember that evil computer? Remember how it took over Max again after his apparent death, and he became the new Lord Havok in the post-Zero Hour: Crisis in Time! League that no one read? Yeah, that's when he turned evil." And then, in Justice League: Generation Lost, Judd Winick says "Well, maybe. But he always disliked metahumans, even if he did grow to care about the particular ones in his team." Note that Johns and Winick were two of the three writers on Countdown in the first place!
When John Byrne rebooted Superman, he wanted Superman to be the only surviving Kryptonian in the DC Universe. His run therefore did not include the Kara Zor-El version of Supergirl, Krypto, the Phantom Zone, the bottle city of Kandor nor Superman's youth as Superboy (which destroyed the Legion of Super-Heroes's continuity).note Byrne has claimed that DC had told him "not to worry about" the effect jettisoning Superboy would have on the LSH (only to then learn DC had no plans to deal with it), and that since his original intent to depict a Superman initially learning the ropes was nixed by editorial, he regrets not having Superboy as an engine to tell those stories. All of these things were brought back by subsequent writers.
Byrne reimagining Brainiac's origin story met such massive fandom outrage that DC quickly began to sweep it under the rug and pretend it never happened until Geoff Johns retconned it in his Superman: Brainiac storyline during his run on Action Comics.
Teen Titans: In Marv Wolfman's original telling of The Judas Contract, Tara Markov was a teenage sociopath who joined with Deathstroke in order to help him kill the Titans, who she loathed for being such "do-gooders". At the end of the arc, she wound dying when she brought the H.I.V.E. headquarters down on herself in a blind rage. In a followup story, she was also confirmed to have murdered Beast Boy's first adoptive father before she'd met Deathstroke, and was always manipulative and a ticking time bomb. Fast-forward to Brad Meltzer's "Last Will and Testament". Meltzer, a self-proclaimed fan of Terra in his youth, decided to retcon the tale and state that Tara Markov was simply a normal innocent girl driven to madness when Deathstroke drugged her. He also changed the details of her death, stating that she'd intentionally committed suicide as shame for her failure. When J.T. Krul wrote the "Blackest Night" tie-in for Titans, he gave a Take That! to Meltzer's retcon by having Beast Boy rage at the undead Terra and ask if she expected him to believe any lies she'd tell him, such as her "being drugged".
In the second issue of the Terra miniseries that introduced Terra #3 (Atlee), Justin Gray and Jimmy Palmiotti tried to explain that Tara's sociopathy was a result of psychosis after she'd been given her powers, with the mineral "quixium" being the culprit. However, these first two issues of the series were written back during 52, when it was originally scheduled to be released before DC had it put on hold. In the time that followed, Meltzer's retcon had passed. Gray and Palmiotti then told readers to forget about their explanation, and refer to Meltzer's version as canonical. The same issue also featured a reference to an event that was to occur at the end of 52, but changed due to overhaul in editorial: Terra 2 was to originally snap and become a villain, and would have to be killed by Atlee (rather than her remaining a hero and being killed by Black Adam in the final product).
Terra 2 was also an example of different writers and editors' intents conflicting. Marv Wolfman introduced her with the intent that she not be the original Terra resurrected, or related to her in any way beyond being surgically altered to resemble her and given powers. After Wolfman left Team Titans, Phil Jimenez began to set up hints that she was at least the Terra of an alternate Earth, but this was quickly shot down by the editors. By the end of New Titans, the editor Pat Garrahy mandated a story that would hint that Terra 2 was the original reborn, which Wolfman hated having to do. Geoff Johns and Ben Raab wanted to go with the idea that both Terras were the same, setting up a story (that went nowhere) where their DNA is confirmed to match. Although when it came to Gray and Palmiotti's miniseries, both characters were established as being separate entities, and the DNA match was explained as the second Terra being genetically altered to resemble the original.
In Wonder Woman: Odyssey Nemisis is the name of the Big Bad while in the previous Wonder Woman volume Diana's love interest was Tom Tresser, aka Nemesis, in a relationship that was nearly universally disliked.
Greg Rucka's run on Wonder Woman (Rebirth) during the DC Rebirth era began with an issue entirely devoted to denouncing many controversial elements of the New 52Wonder Woman comics by Brian Azzarello (such as the infamous retcon about the Amazons replenishing their ranks by seducing and murdering innocent sailors) as the result of propaganda and/or malicious reality-warping.
When John Byrne did Wonder Woman (1987), he'd never had an extended tenure over the character. Thus, a lot of the roll-backs he did were in favor of George Pérez, who'd set the initial tone for post-Crisis Diana; the one he really took aim at was Perez's immediate successor William Messner-Loebs, who'd discarded almost all of Perez's sweeping mythological adventures in favor of Denser and WackierUrban Fantasy. That said, there was at least one point of direct contention between Byrne and Perez: during an early Superman crossover, Byrne had tried to establish the Olympians who empowered Diana were offshoots of the New Gods. Perez disclaimed this in the issue immediately following the crossover, but since he was long-gone by the time Byrne took over Diana's title proper, Byrne doubled-down on the Olympians (and, implicitly, all of Earth's major pantheons) having ties to New Genesis. In practice, this basically made Darkseid a Wonder Woman rogue for awhile, though it was pretty much dropped after Byrne left the title.
The two-part "Continuity Bandit" arc of Kyle Baker's run on Plastic Man took aim at Joe Kelly's run on JLA (1997), particularly the arc about Batman helping Plastic Man reconnect with his son Ernie, by having it state that it is out-of-character for Batman to be willing to frighten a child to set them straight, Plastic Man denying that he ever had a son, depicting Ernie as an insufferably whiny brat and ultimately revealing that what appeared to be Ernie and his mother Angel were actually a disguised J'onn J'onzz and a brainwashed Poison Ivy.
Animal Man: Tom Veitch infamously despised Grant Morrison's run that started the 1988 series and gave a new origin for Buddy Baker's powers that involved a shaman mystically granting them in disregard towards Buddy's previously established origin of gaining his abilities by being revived and reconstituted by the Yellow Aliens after he was disintegrated by energy from their spaceship. Quite tellingly, Veitch's arc began with the shaman smashing clay sculptures bearing the likenesses of the Yellow Aliens as well as Grant Morrison's Author Avatar whom Buddy interacted with at the end of their run. Tom Veitch's changes were since mostly ignored by subsequent writers.
Live-Action TV
There were at least 46 writers for Smallville. Apparent lack of coordination made the show seem to have a very split personality, with wildly clashing tones, contradictory characterisation, and horrendous amounts of Continuity Snarl, and even the writers themselves engaged in their own Ship-to-Ship Combat or promoted their own favourite characters.
that Kon was cloned from Lex Luthor's DNA. Editorial responded in no uncertain terms that this wasn't the case, as Kon's DNA donor was the director of Project Cadmus. Fast-forward to 2003, when Geoff Johns became the writer of the relaunched Teen Titans series with Kon-El as a member of the team, he immediately retconned Kon-El to be a Half-Human Hybrid clone of Superman and Lex Luthor.