Across the Marvel Universe there have been plenty of different villains introduced in many different stories. And due to the multiverse and branching timelines, there have been a lot of stories that have featured these villains having to deal with different versions of themselves. On these occasions it isn't uncommon to see these versions of characters come face-to-face with their counterparts.
Whether it's time travel, alternate realities, misdirection, the battles between villains and alternate versions of themselves proves to be nothing but epic. Always a fantastic display of strength, wit, and character, these interactions sometimes completely redefine these villains in the eyes of the readers, and their motivations and goals are truly underlined, reaffirming themselves in the eyes of the audience.
8 Reed Richards From The Ultimate Universe Is A Maniac
In the Ultimate Universe, Reed Richards helped the world as Mister Fantastic, but after the Fantastic Four split up, Richards descended into madness. He used his superior intellect to try and control the whole world as The Maker, destroying any hero who stood in his way. Becoming completely insane, the Maker became the greatest threat to the Ultimate universe.
The Maker would be pitted against his Earth-616 counterpart during the Secret Wars event. After an omnipotent Doctor Doom created Battleword, the two Reeds joined together to try and restore their universes. As expected, The Maker deceived Mister Fantastic, believing him to be weak and unsuitable for the power Doom possessed. Luckily, the Molecule Man, the source of Battleworld's power, sided with Richards, and The Maker was scattered into pieces into different separate universes.
7 Hydra's Captain America Couldn't Handle The Real Deal
After a piece of the Cosmic Cube manifested itself into an omnipotent girl named Kobik, the Red Skull created a version of Steve Rogers that was completely indoctrinated and loyal to Hydra. The perfect Super Soldier-turned-secret-weapon, this version of Steve Rogers was inserted into the main 616 timeline and executed the Secret Empire event discreetly over the coming months.
Hydra managed to take over the United States, leading a fascist regime and squashing any superhero threats that stood in their way. But when Hydra's Captain America tried to assemble the remainder of the Cosmic Cube them, the Winter Soldier and Ant-Man managed to convince Kobik to return the original Steve Rogers to the timeline. This led to an intense fight between the two Captain Americas, where the original Steve Rogers eventually came out on top.
6 Devil Hulk Is Always Fighting Against The Other Hulks
The Incredible Hulk has changed in persona over the decades, after years of Bruce Banner's complicated relationship with the green gamma monster. Inside Banner's psyche, the Hulk has separated itself into multiple personalities, each one corresponding to a different level of rage, power, and control over Banner's body. One of these versions of the Hulk that has most recently taken prominence in Banner's psyche is the Devil Hulk (or Immortal Hulk).
Despite being an incredibly powerful version of the Hulk that allegedly cannot die, the Immortal Hulk still faces off against the other versions of the Hulk's personality in Banner's mind, such as the Savage Hulk, or Joe Fixit. However, the Devil Hulk is incredibly powerful, and is a greater match for any of the other Hulks. Said to even be stronger than the Green Scar version of Hulk, the Immortal Hulk might just be the strongest there is.
5 Ultimate Cable Had To Slice His Way Through A Broken Timeline
In the Ultimate universe, Wolverine ended up becoming the timeline's version of Cable, the classic time-travelling mutant. In a quest to stop the ancient mutant Apocalypse after he had taken over his timeline, Wolverine-Cable travelled back in time 30 years in order to kidnap Charles Xavier. After attacking the X-Men who came to Xavier's defense, Cable's knowledge of the future made him prepared for everything, easily dispatching the mutants, even his past self.
Eventually, Cable would succeed in taking Xavier to the future, where he would prepare him to fight Apocalypse. Then, when Apocalypse did manifest himself through Mister Sinister, Cable and Xavier returned to the present timeline, where they were bailed out by Jean Grey's use of the Phoenix Force, defeating Apocalypse and most likely erasing Cable's timeline entirely.
4 The Void Is Constantly Fighting Against The Sentry
Robert Reynolds was an ordinary man who, after ingesting a serum meant to replicate the Super Soldier Serum, became the Sentry—a man with the extraordinary power of a million exploding suns. Gifted with this immense power, Robert also became the host to The Void, a dark entity that exploited his enemy's greatest fears, causing Robert great pain and mental torture. The more he used his powers as the Sentry, the more the Void would attack his mind.
While the Void is still a mental manifestation of the Sentry, the Sentry is constantly forced to fight with the Void for control over his mind and body. The complete antithesis to everything the Sentry represents, Reynolds has to carry the burden of knowing that the Void could strike at any time, and the mental fight against the horrible creature is a lonely one, but a fight nonetheless.
3 Knull Is the God of All Symbiotes
During the King In Black event, the symbiote god Knull descended onto Earth, sending out a mass wave of symbiotes that transformed both the Avengers and the X-Men into symbiotes. Knull, the all-powerful symbiote, is known as the source of all symbiotes, making him the original version of Venom, the symbiote controlled by Eddie Brock. Knowing Eddie Brock to be a threat to his rule, Knull made sure Brock was killed early into the event.
After the heroes of Earth were removed from Knull's control, Brock was visited by the Enigma Force, source of Captain Universe's power. With a huge power-up, Brock was revived, and managed to defeat the godly version of his own symbiote, making him the new King in Black.
2 The Skrulls Took On the Avengers In Their Own Backyard
In the Secret Invasion event, the alien race the Skrulls managed to completely infiltrate Earth with shape-shifting warriors, causing mass hysteria and paranoia as the superhuman community came to barely trust one another. This feeling was only fortified when a ship crashed in the Savage Land, and the only passengers were past versions of many Avengers. A fight broke out, with everyone claiming to be the genuine article and not a Skrull.
Some heroes were forced to fight old lovers, old friends, and others were forced to come toe-to-toe with past versions of themselves. Heroes like Spider-Man, Hawkeye, and Luke Cage were all caught in conversations with potential imposters dressed like themselves, but it wasn't until Mr. Fantastic arrived that they learned that the ship was in fact a Skrull decoy.
1 Stryfe is Doomed To Fight Cable Forever
Stryfe is the clone of the mutant Cable from an alternate future where the mutant Apocalypse ruled. After Nathan Summers was infected with the techno-organic virus as a baby, a woman from the future offered to take the baby into the future, where the technology was available to keep the baby alive. Once the baby was brought to the future, he was cloned, but Apocalypse found the child, and decided to raise him himself as Stryfe.
Stryfe would come face-to-face with his clone Cable many times over the years, as both would lead opposing sides in the long-drawn-out war for their ravaged future. Most recently, Stryfe was found to be alive in the Cable solo series, where Stryfe had been kidnapping mutant babies, looking to use them as part of a ritual sacrifice. Once again, he was thwarted by not just one version of himself, but two, as the original, older version of Cable was resurrected for the fight.