Redemption within fiction often reflects humanity's desire to better themselves and gives hope that anyone can atone for any sins that they have committed in the past. Fans of superheroes especially love seeing villains becoming heroes, and the proof is seen across the Marvel Universe. Multiple heroes used to be on the opposite side of the law, with some ex-villains acting as some of the biggest heroes in Marvelーfrom Black Widow and Hawkeye beginning as Iron Man villains before being convinced to become superheroes.
Sometimes fans forget that some popular heroes used to be villains, and sometimes they don't recognize how vital their redemption arc is in the grand scheme of the Marvel Universe. What would the comics or movies be like if characters like Rogue or the Scarlet Witch never become heroes? It's a what-if scenario that most fans probably don't even want to dare think about, and it is best to be reminded of all the successful times a villain turned into a hero.
10 Songbird
At the end of the Onslaught mega-crossover event in the late 90s, many Marvel heroes vanished. In their place came the Thunderbolts, a team of superpower individuals who -gasp- turned out to secretly be villains in disguise. However, in a twist of fate, the villains actually liked being heroes, and most remained that way full time.
No one character exemplifies the Thunderbolts more so than Songbird. Once, the minor villain that went by Screaming Mimi's name, Melissa Gold, was never a viral character before Thunderbolts. But because of the team, Melissa as Songbird has endured becoming one of Marvel's most beloved female heroes.
9 Rogue
Rogue is such a vital member of the X-Men that most fans don't remember, or even realize, that she first appeared as an Avengers villain. In her initial appearances, she worked with Mystique and the Brotherhood of Evil Mutants. She fought against multiple Marvel heroes, most notoriously against Carol Danvers, who went by Ms. Marvel back then.
Rogue was able to absorb the powers of Ms. Marvel, gaining flight, super strength, and invulnerability. Not long after her fateful fight with Ms. Marvel, she will leave the Brotherhood and join the X-Men, becoming a mainstay ever since.
8 Scarlet Witch & Quicksilver
These twin superheroes started as Magneto's Brotherhood of Evil Mutants, though they were reluctant members. Magneto saved their lives in a fire, so Wanda and Pietro Maximoff felt indebted to serve the mutant.
The two didn't stay on the Brotherhood for long, as an alien being kidnapped magneto and the rest of the Brotherhood became inactive. Feeling they no longer owe Magneto for anything anymore, the two would then join the Avengers. They have been mainstays ever since, and now Wanda is set to star in the upcoming WandaVision Disney+ show.
7 Hawkeye
Another reluctant villain, Hawkeye, was manipulated by Black Widow to fight against Iron Man. After a few scuffles with the Iron Avenger, Hawkeye decided to go straight. He then became an Avenger, along with other former villains Scarlet Witch and Quicksilver. He has since evolved past his villainous origin and has become more of a smart-aleck hero.
Hawkeye's mouth may get him into trouble with both villains and heroes, but deep down, most characters know he's a good person. He's now a major Avenger within the MCU, with his own Disney+ series on its way.
6 Black Widow
The 60s were a different time. America was deep into the Cold War, so Soviet Union villains were all the rage back then. Spy properties were also viral back then, thanks to the properties like James Bond and the UK Avengers TV show (no relation to Marvel's Avengers).
Black Widow was created as a direct response to both the Cold War and spy movies. She was a Soviet spy who came to America to take down Iron Man. She eventually defected from the Soviet Union and has been a major Avenger since then. She'll be starring in her own movie coming hopefully next year.
5 Magento
Magneto is one of Marvel's greatest villains, yet he's also a character who often swings back and forth between outright villainy and true heroism. Magneto is a Holocaust survivor, who after witnessing his own kind being pushed to extinction as a kid, decided he didn't want the mutant race to suffer the same fate.
Magneto genuinely wants what's best for mutant-kind, which often explains why he has such a wishy-washy stance on villainy. Magneto sometimes has to be the villain to protect his race from ignorant humans.
4 Dr. Octopus
This was a heroic turn that almost no one saw coming. As the decades past, comic authors began writing supervillains with more nuance. Villains became less cartoony and more complex, no longer acting as one-dimensional caricatures. With that said, Dr. Octopus remained one of those villains that stayed as a one-note baddie.
So fans were in a huge surprise when the good old Octopus took over the body of his nemesis, Spider-Man, and became the self-labeled hero, the Superior Spider-Man. While extremely controversial when it initially began, the Superior Spider-Man run of comics ended up being a fan-favorite storyline.
3 Emma Frost
Emma Frost is one of those heroes that even when she is doing something heroic, she doesn't necessarily do it in the nicest way possible. In fact, Emma may be in the running for being one of the least likable heroes in Marvel's pantheons. The ultimate Queen Bee, Emma, sees everyone as lesser than her, and she makes sure everyone knows it in the wittiest way possible.
It's no surprise that she started as a supervillain, having been the White Queen for the Hellfire Club before joining the X-Men. Even after joining the sides of the angel, Emma acts as anything but an angel.
2 Deadpool
Deadpool isn't really a hero per-say. He is more of an anti-hero. However, before he officially became an anti-hero, he was a straight-up supervillain. A mercenary with super-healing capabilities, the Merc with a Mouth first showed up within the pages of New Mutants as an assassin. Even though he was a smart-aleck from the get-go, he wouldn't evolve into his more zany personality until later down the road.
After a few decades of his debut, Deadpool is now one of Marvel's most cherished anti-heroes. He may do a lot of bad stuff, but deep down, Deadpool is just a lovable goofball.
1 Venom
Serving as a dark analog for everyone's favorite web-slinger, Venom grew too popular to be another Spider-Man villain. Because fans grew to love him so much, he outgrew Spidery's shadow and ended up starring in his own series of books.
He was originally Marvel's go-to anti-hero, however as the years pass, he's grown more and more heroic. He is currently siding with the Avengers to face off against the oncoming onslaught of Knull, the King in Black.