In several of the early comics, the Hulk was slightly more intelligent and could talk better, barely even referring to himself in the 3rd person. Then eventually this paved way to the more popular dumb beast that always spouted "Puny human make Hulk angry! Hulk smash!" Though later retcons would establish that this behavior was still canon. The Hulk has multiple personalities, with some of them being quite intelligent while others are just mindless, screaming monsters.
She-Hulk debuted with the same brutish Hulk Speak as her cousin Bruce and while more attractive she was supposed to be seen as a monster like him. It wasn’t until towards the end of her original run before she joined the Avengers that Shulkie spoke in full sentences and displayed a clear intellect in her Hulk form. Her tongue in cheek fanservice and Breaking the Fourth Wall humour that she’s best known for wouldn’t come until John Byrne started writing her in the 80s.
Betty Ross was originally a simple Nice GirlLove Interest who was warm and affectionate. A far cry from the cynical and harsh Broken Bird that most modern readers are familiar with now. Though in absolute fairness a Trauma Conga Line (including cancer, miscarriage and demonic rape) will do that to you. Later retcons to her past retroactively make Betty more assertive rather docile as she was when first introduced.
While always quite the prick, General Thaddeus Ross in the early comics wasn’t nearly the despicable tyrannical hypocrite hated by pretty much everyone including his own daughter. If anything classic Ross operated similarly to J. Jonah Jameson, to wit he was a constant thorn in the side of the protagonist (Bruce)’s alter ego but still showed genuine care to his allies and family. Later comics however took Ross’s Moby Schtick so far that he was willing to become a Hulk himself to kill Bruce and before that even stormed Betty and Bruce’s wedding armed with a gun.
The Thing has a very distinctive "voice", with most of his dialogue carrying a rough-and-tumble lower-class vibe, befitting a guy hailing from the Lower East Side of Manhattan. In early issues, though, this trait was mostly absent, with his lines sounding noticeably more formal and stilted, even a bit villainous, saying things like "bah!" and "fool!" In general, he came across as less of a Jerk with a Heart of Gold and more like a Token Evil Teammate, with him being actively disdainful of civilians and creating by far the most collateral damage.
Captain America wasn’t the idealistic paragon of virtue in his WWII comics, being meant to appeal to 1940s American youth and soldiers Cap was very much “one of the boys” i.e Hot-Blooded, rude and shockingly immature in his Steve Rogers persona. For example Cap would routinely pull pranks and humiliate his sergeant just for fun, being more like the guy who bullied Steve in the 2011 film. Modern era Captain America would retcon this behaviour as an act to keep Steve’s secret identity intact. Classic Cap also displayed multiple prejudices and made racist remarks to Asian people and black people — whereas numerous retellings have Steve display compassion to other races and culture ahead of his time.
Iron Man in his early comics was actually pretty different from the snarky, womanising, recovering alcoholic Broken Ace genius that most fans are familiar with. Tony in the early comics was actually pretty friendly and polite instead of being a Jerk with a Heart of Gold. Noticeably rather bedding heaps of women, Tony was actually terrified to have a relationship with the shrapnel in embedded in his heart, believing he could die any day. Tony’s dual lives also played a big part of his character, whereas most modern fans are used to Tony having no secret identity whatsoever. Tony’s more affable attitude in beginning is also reflective in the fact Stan Lee created him as a bet that he could make a sympathetic hero out of Arms Dealer millionaire, somebody a 60s reader would despise. While modern comics ironically go in the other direction and lean into Tony’s unlikeable qualities for the sake of drama.
Thor in his early comics wasn’t a really character on his own but the persona Donald Blake would on after he found Mjölnir in a cave. It wasn’t until later they established Donald Blake was Thor all along (with a one modern Thor arc having Blake be an Enemy Without). Early Thor also had Ye Olde Butcherede Englishe on maximum while modern Thor speaks relatively normally beyond the usual “Thou” and “Doth”.
Black Widow wasn’t a spandex wearing She-Fu happy Action Girl assassin when she first debuted in the pages of Iron Man. Classic Natasha was more like a typical evil Femme Fatale Bond girl who would use feminine whiles and cunning as well as subordinates to get the jump done. There was some hint towards her being a sympathetic character with Tony feeling pity for her, but otherwise she was unambiguously evil. It wasn’t until her relationship with Hawkeye that it was revealed she was brainwashed by the KJB and even later still that she would join the Avengers and become a hero. Further retcons would also reveal she had been given a Super Serum that slowed her aging and she always a master combatant — something that wasn’t apparent at all in her early appearances.
Hawkeye in his first appearance was nothing like the loveable underdog Badass Normal most fans know and respect. Clint has in his debut was more like Corrupted Character Copy of Green Arrow with his reasons to dress up and fight crime being quite unheroic. Namely Clint was jealous of the attention Iron Man was getting and when the aforementioned Black Widow bewitched him with her charms and tasked him with killing Iron Man, which Clint eagerly hopped to without the slightest moral qualms. That’s right he was willing to commit outright murder simply because he was so horned up over one hot babe! It was only in subsequent appearances did Hawkeye evolve into the more likeable character who wouldn’t willingly take a life. Clint was also a genius inventor in his debut and sought to take Tony’s technology for his own, in comparison to later comics where Clint is befuddled by the Technobabble Iron Man and other scientist superheroes speak.
Ant-Man (Hank Pym) and The Wasp (Janet Van Dyne) were wildly different in their first appearances from the modern versions of their characters. Hank didn’t begin as a superhero, rather just as some schmuck who foolishly poured a shrink serum over himself and got stuck in an ant-hill, he even poured the serum down the drain after getting back to normal size, swearing he would never use the formula again… something he clearly didn’t hold to. As for Janet she wasn’t the sensible Team Mom and Iron Lady seen in modern comics rather a highly flirtatious and vapid young woman who didn’t take her role as superhero that seriously.
Carol Danvers in her early comics wasn’t a militaristic Hot-Blooded feminist Flying BrickAction Girl. Indeed original Carol was largely a skittish Girly GirlLove Interest to Mar-Vell who used her job as head of NASA security as an excuse to pursue Mar-Vell romantically and frequently become a Damsel in Distress. It wasn’t until she became Ms. Marvel would Carol shift into the tough and powerful personality fans are familiar with. Even Carol’s ace pilot background was a later addition long after she was introduced.
Hannibal King, friend of Blade, was originally introduced in The Tomb of Dracula as a no-nonsense private eye who tended to stay calm, unobtrusive, and most professional. In Night Stalkers, he became very emo, angsty, and melodramatic. And in later appearances, he became a goofy, bumbling, comic relief punching bag. This third characterization may be a response to Blade: Trinity and Ryan Reynolds' characterization of King.
The Chaos King, A.K.A. Amatsu-Mikaboshi, did not speak entirely in haiku in his first appearance. It was only in The Incredible Hercules that this bit of characterization was introduced, and he's spoken this way ever since, because it just sounds cool. One wonders why a "Chaos King" would take the effort to speak in such orderly fashion, but as the man (or primal chaos-being) said himself:
''The contradiction / is what makes it so very / chaotic, get it?"
Before becoming Moonstone, Karla Sofen was introduced as a scantily-clad gun moll for the Captain America villain Doctor Faustus. There was also no hint of the cunning and manipulative personality she would later become known for.
UltimateNick Fury was a lot different in his initial appearance, being more like Tony Stark (i.e. a suave, cocky and insanely rich ladies man) than the stoic Samuel L. Jacksoninspired character who later appeared in The Ultimates.
