Superman's entire history says a lot about this trope. Originally his powers didn't come from the rays of Earth's yellow sun, but were genetic since Krypton was home to a "race of supermen"; the horrors of World War II put an end to that kind of praise of eugenics. As has been well-documented, Superman did not originate as much of a "boy scout" (thus making it ironic when people say, "there's no room for a boy scout, this isn't 1938 anymore") and was distrusted by and distrustful of authorities, while his adventures pitted him against people abusing the downtrodden. During World War II, he moved into the role of "boy scout" and was often depicted as fighting enemy spies to the point where by the end of the decade, he was frequently depicted in front of the American flag, and so-forth. Then, of course, by the fifties, everything about him seemed to change to suit the atomic age, from his powers, to his ideals. This, however, didn't stop him from occasionally tackling common prejudices of the time in which he has to battle an expy of the KKK who were threatening a Chinese-American family.
Values dissonance began to haunt Superman by the end of the '60s as he had not reverted to his earlier, rebellious form, but remained a symbol of the establishment, despite the youth movement moving that way. Attempts at "modernizing" Superman were often scoffed at, and between the '70s and the '00s, Superman was often used as an example of the right and virtuous old-fashioned superhero for better or worse, though besides "I don't kill," they're rarely specific about what "morals" of his are supposed to be outdated. That's not to say Superman never had any high points during this period, they just tended to be more about the overall plot or spectacle. Lately, they seem to be trying to get away from this.
Many Superboynote Superman in his youth comics had the main character, Clark Kent, being subjected to corporal punishments, usually in the form of spanking, by his adoptive father, Jonathan. However, Jonathan discovers the hard way why he would be called Man of Steel, even with a spanking machine, which is also destroyed. One story even has it in a school! Now, think about that for a moment considering corporal punishment of any kind in school... at least state ones, would not go well with today's view.
One 1950s storyline has Lois Lane breaking Superman's absolute veto about following him to the Fortress of Solitude. The storyline attributes this not to her being a journalist but down to her being female, and therefore both nosy and in need of punishment for this very female character flaw. Superman, watching unseen, orders the sentinel robot to catch her and inflict Punishment. The robot therefore upends her over its lap and applies a vigorous spanking. The next morning she apologises to Clark Kent about not being able to sit down "because of what that robot did to me last night". The reader is invited to join in with the laughter.
Shortly after Supergirl's introduction, there's a Superman story in which (for typically contrived Silver Age reasons) he has to pretend to be engaged. So, he spends a good part of the story making kissy-face with the mysterious new superheroine Mighty Maid. At the end of the story it's revealed she's Supergirl in disguise, and thus Supes has been making out with his 15-year-old first cousin. (A later story makes it clear that this is not Kryptonian-Earth values dissonance; first cousins couldn't marry on Krypton.)
Many modern collections of Golden Age stories have taken steps to try removing content that would be deemed offensive. For instance, many of the Wonder Woman collections remove the painfully racist caricatures of black people, replacing them with more natural-looking black characters.
Wonder Woman from the Golden Age had a particular problem because her creator, William Marston, believed that dominance, submission, and a very bondage-oriented culture were all things needed in what was then "today's world". Wonder Woman at one point extols the virtues of being a (consensual) slave. Needless to say, this sexuality-based cultural paradigm was not in synch with what people believed then, and hasn't really caught on now either. And while Marston had very progressive ideas about women's empowerment for his day, he also seemed to think that women were "naturally" prone to things like vanity and emotional outbursts.
Much like the Bat Masterson example in the television section, many older comics, including ones featuring Superman and Batman, had the heroes sometimes punish female criminals by spanking them. This is even where Batman's infamous "quiet or poppa spank" line comes from. By today's standards, it'd be considered sexist, as well as sexual harassment.
Two-Face's traditional origin of his disfigurement being the cause of his Face–Heel Turn has been criticized as being in poor taste due to implying that deformed people are inherently evil. Adaptations have tried to mend this to varying degrees:
The Post-Crisis comics, the DC Animated Universe and Batman: The Telltale Series depicted Harvey as suffering from mental health issues long before he's disfigured (though given the type of games Telltale did, the player can save Harvey from his disfigurement and he'll still snap).
The Batman combined Two-Face's origin for the character of Clayface due the Bat Embargo making Two-Face exclusive to the below film. However, not only is Clayface’s body warped, but he was subject to psychological torture from Joker and constant abuse by his Bad Boss, finally being unable to take any more of it. Even then, he was simply on a tipping point and people treating him like a monster was the straw that broke the camel’s back.
The Dark Knight had his disfigurement be combined with the death of Rachel Dawes and both be the capstone of a Trauma Conga Line Harvey went through.
Beware the Batman, Batman/Tarzan: Claws of the Catwoman, Harley Quinn (2019), DC Comics Bombshells and the Grim Knight's universe shown in the Batman Who Laughs miniseries depicted Harvey's moral compass as largely unchanged: the former three went with Adaptational Villainy and had Harvey be a piece of work long before he's disfigured, whereas the latter two went with Adaptational Heroism and keep a disfigured Harv on the side of the angels.
An in-story example occurs in Infinite Crisis, when '70s superhero Black Lightning meets modern black superhero Mr. Terrific. Terrific remarks that a black person actually calling himself "Black Lightning" is ridiculous. (He did wear a black-and-blue costume, and his lightning bolts are often depicted as literally black, but still.) Lightning replies that when he began his career he was "the only one of us out there" and wanted people to know that.
The climax of an early Constantine story dealing with a serial killer, the Family Man, who targeted Constantine involved getting a gun. Given that the killer is a knife-wielder, the confrontation is a bit uneven. For a British audience, the pistol was presumably an unexpected and shocking twist. For any nation where pistols are perfectly legal and commonplace, this is both an Anti-Climax and idiotic moment for Constantine who did not think to use a gun on many previous occasions and treated the mundane weapon with more disdain and disgust than literal infernal tools.
Writer James Robinson talked about this when explaining some of the character changes in the New 52 reboot of the JSA. He pointed out that while the team's all-white, all-heterosexual (and mostly male) line-up was to be expected back in the Golden Age, there was no excuse for it remaining that way in 2012. To that end, he slotted in the black Mr. Terrific and the Latina Hawkgirl as founding members of the team, and made Alan Scott/Green Lantern an openly-gay man.
DC Comics trend of returning characters from the Legacy Character inheritors to the versions the writers grew up with has had the unintended consequence of removing/killing off dozens of minority characters from the DCU. Because back when they were reading, all the major heroes were white.
An odd version of this occurs with the Flash (Barry Allen). Barry was previously treated as something of an optimist and a good-natured fellow, with cheerful science lessons for the readers. In the decades since his death, this almost became Flanderization, with Barry being treated something close to a saint whose only flaw was spending too much time on heroics, showing up late on dates with his wife. The problem with his return? Barry was intended to be a nerd hero, so his day job was a police scientist. In the 1950s, nobody thought much of it. In 2010, CSI, profiling, and forensics investigations are the subject of nightly television drama, so Barry's happy attitude was jarring on a character who'd retroactively seen more death than the Joker. Although there is such a thing as Gallows Humor; it's common for people in jobs like Barry's to develop strong (albeit often somewhat dark) senses of humor as a psychological defense mechanism to counteract the grime and misery they're confronted with on a day-by-day basis in their careers. This tends to not make it into said dramas because angst is generally more dramatic and makes those involved seem less insensitive. And with an increasing number of more comedic elements in forensics shows (Autopsy Snack Time, just as an example), the modern reaction to this is ITSELF subject to this trope.
Green Lantern Hal Jordan premiered in the late 1950s with a female boss/love interest who ran a military-industrialist complex air base, and an Inuit sidekick who not only knew his secret identity, but kept Jordan's power source safe and even stood in for him when Jordan was off-world. These concepts were quite progressive at the time, but to modern readers get easily overshadowed by his boss turning to supervillainy to try to force Green Lantern into marriage (granted, due to periods brainwashing, but she still jumped through hoops to try and get him to marry her outside of that) and his sidekick gleefully accepting a blatantly racist nickname. Fortunately, in the latest reboot, the nickname "Pieface" showed up only on one occasion, and got the speaker pummeled shortly thereafter.
Hal's behavior towards Carol is also something heavily dated, as he would constantly ask her out despite her constant refusal due to it being inappropriate to date an employee. There it was just to make a typical superhero love triangle but nowadays makes Hal look like a textbook sexual harasser.
Watchmen: One that actually works in Alan Moore's favor is Rorschach calling New York City "an abattoir of retarded children". At the time, "retard" wasn't considered that offensive, but in the time since, especially after a certain scene in Tropic Thunder, it's become a highly offensive term, so it will turn more modern readers off on Rorschach rather than having them become part of the Misaimed Fandom that arose when the story first saw print.
In The Judas Contract from the early 1980s, The Mole Terra has a sexual relationship with Deathstroke. Not only is Deathstroke twice her age, but he has kids either her age or older. Terra is above the age-of-consent in most of America (she was sixteen) however it's still squicky. That was the intended reaction, however it's become a bit too uncomfortable in future years. That aspect of their relationship either gets altered or criticized in adaptations and future references. The 2003 Teen Titans (2003) cartoon and Young Justice (2010) outright removed their relationship (with it depicted as more of a mentorship in both) and the 2016 animated film adaptation of the arc also changed it so that no sex occured. Terra simply has an unrequited crush on Deathstroke. The main bone of the problem is that the original story tries to use the relationship to show Terra as wicked and depraved, while ignoring how sleazy it makes Slade look like. When having an opportunity to Retcon the relationship away, the DC RebirthDeathstroke series shows it happened but portrays it as something Slade has done to more easily manipulate and control Terra, a Moral Event Horizon even for Deathstroke himself, that seriously messed the already emotionally unstable Terra up for the rest of her life, and The Other History of the DC Universe, when discussing the events of The Judas Contract, openly denounces Deathstroke as a pedophiliac rapist.
Camelot 3000, released in the mid-80's, features Sir Tristan, a male knight reincarnated in a female body. The Supporting Protagonist Tom Prentice is attracted to Tristan's female body and is constantly making moves on him, referring to him as a woman and calling him "Amber", the birth name of his female incarnation. This was depicted as Tom being a Dogged Nice Guy at the time, but in the 2020's we recognise that Tristan is effectively a heterosexual (as he's still in love with Isolde) transman; who Tom, a cis/het guy, is relentlessly sexually harassing, misgendering and deadnaming.
