Ant-Man: The Irredeemable Ant-Man, Eric O'Grady, was this to the original Ant-Man, Hank Pymnote not without his own problems - see Once Done, Never Forgotten. O'Grady got his costume from stealing one of Pym's, and is an often lecherous, cowardly, and amoral man who nonetheless had some positive traits and often wished he was a better person. Not to be confused with Scott Lang, who while also stealing the Ant-Man suit, only did it to save his daughter and was really sorry about it - if anything he was more heroic than Pym. O'Grady eventually got killed off (albeit in a Heroic Sacrifice to save a child) right around the time Marvel decided to bring Lang back.
Black Panther: Kasper Cole briefly took the name for some reason or other, and fights crime and junk and stuff. Used guns for a while.
In The '80s, Steve Rogers, the original Captain America, was replaced by John Walker, a '90s Anti-Hero version of himself. To his credit, Walker did eventually make an honest effort to emulate Rogers' ethics until the Red Skull completed his manipulation of him. When Rogers regained the mantle, Walker continued operating as the U.S. Agent. In something of an inversion from the previous examples, the Darker and Edgier Walker wore the classic red, white, and blue Cap outfit, while Steve took up a black costume and shield as The Captain.
Like Knightfall this was apparently a deliberate in-your-face. And the same thing happened with Bucky Barnes as Captain America. That said, Steve went on record in Heroic Age: Superheroes that there's not a man out there more fit to wear those colors than James Buchanan Barnes.
It should be noted that during Bucky's tenure as Cap, while he did use his gun and his costume did invoke a Darker and Edgier anglenote the costume had far more black than the red, white, and blue., the main conflict for Bucky was whether or not he could do right by Steve Rogers as Captain America. As such, Bucky would act as best of a hero as he possibly could during that amount of time as Cap.
Dark Avengers: Most of Norman Osborn's Dark Avengers were villains that had their costumes redesigned to look like familiar heroes (Bullseye as Hawkeye, Moonstone as Ms. Marvel, Venom as Spider-Man, Daken as daddy Wolverine). He went a bit overboard on this front during the Dark Reign, creating the Dark (now Shadow) X-Men, making the HAMMER organization to replace S.H.I.E.L.D., and forming The Cabal, essentially a copy of the already morally ambiguous Illuminati, as well as his own Initiative with The Hood and his gang.
Fantastic Four: Intentionally done in The '90s, when the Fantastic Four were presumed dead, and Spider-Man, Wolverine, The Hulk, and Ghost Rider took their places, swearing to avenge the heroes' deaths. Only three of the four were really Anti Heroes, but the extremely ill-suited-for-eachother group fought amongst themselves so much and were so bad at emulating the FF's legendary teamwork that Spidey was pretty much ineffectual in getting them to shape up and the whole team made the Fantastic Four's dysfunctional family dynamics look incredibly well-adjusted by comparison.
Marvel played homage to that story a few years ago with even more antiheroic versions of those four - the abovementioned Red Hulk and Ghost Rider's Distaff Counterpart Alejandra, X-23 and Flash Thompson's Venom (Redeeming Replacement to previous Venoms, but much more antiheroic than Spider-Man; he's a US Army soldier rather than a Thou Shalt Not Kill type superhero).
Ghost Rider: Vengeance is an odd example. While Ghost Rider was already an Anti-Hero, in the nineties, a character named Vengeance showed up who was supposed to be a Darker and Edgier version of a character that was already the epitome of Darker and Edgier. A new Vengeance has since appeared — as a villain. And the de-powered original Vengeance seems to be a pretty nice guy these days.
The Incredible Hulk: The Hulk has both subverted and played this trope straight at the same time. After World War Hulk, with the Hulk imprisoned by the army, his series was taken over by Hercules and a new series was launched with a mysterious Red Hulk as the central character. The Incredible Hercules subverted the trope quickly, proving he's anything but an Anti-Hero, while Red Hulk played it straight, acting like a total dick and making Hulk lose his powers.
Earlier on in the '80s this trope popped up, with the normal destructive but rarely malicious green Hulk being replaced by an amoral jerkass grey Hulk named Joe Fixit. Green Hulk is an anti-hero to begin with but the trope still stands as Joe Fixit is several notches down the scale. The twist is Joe Fixit is just another of Bruce Banner's repressed personalities.
And while we're on the subject: Dr. Leonard Samson was a nerdy little nebbish scientist who managed to de-Hulkify Hulk, turning him back into Bruce Banner. He then used a portion of the stored gamma energy to turn himself into Doc Samson, who wasn't really an anti-hero so much as he was just kind of an egotistical jerk. When he started wooing Betty, it convinced Bruce (who was initially thrilled to be himself again) to use the rest of the stored gamma energy to turn himself back into the Hulk.
Tony did this to himself, in a way. When his suit was damaged, he built the War Machine armor. Not only did it have the appropriate Darker and Edgier name but it was loaded with BFGs and was colored black and gray. Stark wore the armor in a few issues, invoking this trope even though it was the same guy in the armor. After that arc, he gave it to Jim Rhodes, who is actually a bit nicer than Stark. It should also be noted that Rhodes replaced Tony as Iron Man for a couple of years due to Stark's alcoholism so in a way, it was an inversion of this trope.
After being rendered comatose at the close of Civil War II, he was replaced by two characters. The main Invincible Iron Man book was taken over by a teenage girl named Riri Williams, who would eventually become known as Ironheart. The second book, however, was Infamous Iron Man, which starred the former Doctor Doom in a new suit of Iron Man armor as he tried to become a hero.
Iron Man 2020 (Event) stars Tony's brother Arno Stark, a vicious anti-hero who takes over as the new Iron Man after Tony comes to believe he died during Civil War II because of the nature of his current body.
In an inversion, Thor was replaced by Thunderstrike a.k.a. Eric Masterson in The '90s, except Thunderstrike was less likely to kill a dangerous opponent and he came across as a dork when he tried to sound like an anti-hero. Thunderstrike did however, look the part. Complicating the whole thing was that Thunderstrike had previously been Thor himself.
Also downplayed by Beta Ray Bill, who was somewhat more merciless compared to Thor but otherwise still a noble and courageous soul.
Played a bit straighter with Eric Masterson's son, Kevin Masterson. Not long after inheriting his father's Thunderstrike Mace, Kevin becomes the second Thunderstrike. While not even remotely evil or anything, being a young teenager in a slightly aged-up alter-ego body who was struggling with the loss of his father (who he felt was largely abandoned by the Avengers) definitely lends him to be more superficially anti-heroic than his dad was.
As of mid-2017, there are three Thors running around. The Odinson himself, Jane Foster (wielding Mjolnir), and the "War Thor" - a traumatised Volstagg wielding Ultimate Thor's hammer. The first two are straightforward heroes, but the third is very much this.
Narrator: Behold the War Thor, and prepare to bleed.
Spider-Girl: After being severely beaten, Spider-Girl briefly had her place taken by her crazed clone April. April later pulled a Heroic Sacrifice to save the original Spider-Girl.
Venom could count as a rare villain-to-villain example of this. Eddie Brock, the original Venom was certainly a homicidal maniac, but he eventually was tailored into a '90s Anti-Hero of sorts. The third Venom, Mac Gargan (the Scorpion) is more evil than Brock and thus since he pretends to be a hero as part of the Dark Avengers, he's both an Anti-Hero Substitute for Spider-Man (who he impersonates) and Venom. The second Venom (Angelo Fortunato) didn't last long enough to be considered a substitute. Once Flash Thompson became Venom, you could argue for it being an odd reverse villain-hero example; Flash being more heroic than Eddie at his very best. And then it went back to anti-hero again as Eddie.
Zig-zagged in The Clone Saga. The original aim of the series, itself a continuation of a Silver Age storyline, was an attempt to roll back the creeping cynicism of the nineties. Whilst Peter Parker continued to spiral ever downward into depression and anger, Ben Reilly was introduced as a Lighter and Softer Spider-Man with the same set of memories as the original, a powerful statement of just how far Peter had fallen.
The entire premise of Superior Spider-Man (2013), which sees Otto Octavius a.k.a. Doctor Octopus becoming a Darker and Edgier Spider-Man after performing a "Freaky Friday" Flip with Peter Parker and then leaving him to die in Ock's frail body. As Spider-Man, Otto spies on criminals 24/7 with automated "Spider-bots" equipped with cameras, employs a private mercenary army called "Spider-Patrol 7", and even has his own force of eight-legged Humongous Mecha decked out in Spider-Man's classic red and blue. Notably, where Peter was the classic Hero with Bad Publicity who was frequently treated as a criminal nuisance by the cops and the press, Otto frequently gives orders to the police and city hall.
Ezekiel Sims has similar powers to Peter and a desire to do good, but is often more selfish, cowardly and willing to cross moral lines. Though he at one point attempts to sacrifice Peter to save himself, he does have a Heel Realization at the last minute and instead makes a Heroic Sacrifice to save Peter.
The Ultimates: Inverted. Monica Chang, the second Black Widow, is far more pure and upstanding than her predecessor, who killed children in cold blood and was secretly The Mole to a super-powered terrorist army that takes over the United States in one arc before being killed. After Monica dies in Ultimatum, a third Black Widow (the Peter Parker clone known as Jessica Drew/Spider-Woman) takes over, and is equally heroic.
X-Men: While she never adopted the name or costume, Emma Frost essentially became this to Jean Grey after the latter's death in New X-Men, replacing her as the team's resident telepath, the Institute's headmistress and Cyclops' bedmate. This was a status that she was aware of and more than one character (including a teenage Jean) has needled her about it.
