My Hero Academia is a popular superhero anime series, and its characters could easily step into similar superhero worlds and get the job done, such as in the realm of Marvel comics and certainly the MCU. Many pro heroes could join the Avengers as front-line fighters or support characters, but so could the villains of MHA.
Realistically, most villains in MHA would join the mad titan Thanos or the trickster god Loki, but if the villains repented and changed their ways, some of them could actually earn a spot among the Avengers and finally start fighting for good instead. Or at least, they could join the Avengers in exchange for avoiding jail time and help defend their beloved Earth from invading aliens.
10 COULD JOIN THE AVENGERS: Himiko Toga Can Spy On Earth's Enemies
Himiko Toga can use her Transform Quirk to mimic other people, including their voices, if she ingests a sample of their blood first. She often uses this ability to spy on the pro heroes or stalk Izuku and Ochaco, but she could put her talents to use for S.H.I.E.L.D. if circumstances allowed it.
Himiko would become the second Black Widow, infiltrating Hydra and other villainous groups while under disguise to collect information and even assassinate key enemy leaders. Himiko is highly acrobatic and good with knives, meaning she could dispatch a few targets and then slip away.
9 COULDN'T JOIN THE AVENGERS: Muscular Is Just A Worse Hulk
The Avengers already have a brute-force fighter on their side - the Incredible Hulk, the massive green alter ego of Dr. Bruce Banner. If other warriors join the Avengers, they need to offer something that the Hulk cannot, such as Thor and his lightning.
Unfortunately, Muscular is simply a scaled-down Hulk, a melee fighter who can greatly enhance his muscles with his Quirk. He's strong, but the Hulk is stronger. Even if Muscular repented for all his heinous crimes, Nick Fury still wouldn't recruit him.
8 COULD JOIN THE AVENGERS: Overhaul Is Incredibly Useful
Overhaul is a massively talented villain who helped lead the Shie Hassaikai criminal organization and defeated Mirio Togata/Lemillion in battle before he took on Izuku and very narrowly lost. In battle, Overhaul can use his Quirk of the same name to reshape any matter, living or not.
Overhaul can blast people apart with a touch, or conversely, heal them. He can also reshape the walls or floor to create barriers or spikes, or repair objects with a touch. The Avengers could find endless uses for Overhaul if he behaves himself.
7 COULDN'T JOIN THE AVENGERS: Moonfish Isn't Really Needed
One of the creepiest League of Villains members is a fellow codenamed Moonfish, who is always seen bound up in black leather outfits. Only his mouth is exposed, so he can elongate his sharp teeth with his disturbing Quirk. He can even prop himself up with his elongated teeth and use them as legs.
Moonfish can stab his tooth-blades all over the place, but his firepower isn't especially great, and he would be an awkward fit for the Avengers even if he wanted to switch from villain to hero. He's not exactly inspiring in battle, either.
6 COULD JOIN THE AVENGERS: Kurogiri Can Teleport People With Ease
Kurogiri is a support member of the League, and he is also an advanced Nomu made from the remains of Oboro Shirakumo, a former U.A. student. Kurogiri is best known for using his Warp Gate Quirk to rapidly teleport people all over the place, even from across great distances.
The Avengers could make excellent use of those gates to rapidly raid enemy strongholds and escape just as quickly, no helicopters needed. Kurogiri's gates can also be used to redirect enemy attacks and thus protect his fellow Avengers.
5 COULDN'T JOIN THE AVENGERS: Trumpet's Quirk Isn't Needed
The Meta Liberation Army has many talented members of its own, and that includes a well-dressed fellow calling himself Trumpet. He can use his voice-based Quirk to motivate and empower the people around him and give them a power boost. It is best used with mobs of low-level allies who need extra strength for a real fight.
The Avengers don't need this kind of Quirk at all. Each Avenger is already brave, confident, and motivated to fight evil, and Trumpet's Quirk is rendered moot with them. Besides, Trumpet has no means of defending himself, and his offensive power is low.
4 COULD JOIN THE AVENGERS: Hekiji Tengai Can Limit Collateral Damage With His Barriers
Hekiji is one of the Eight Bullets, elite agents who fight for Overhaul. They are all perversions of Buddhist principles, but at least Hejiki rarely sheds blood in battle, unlike his fellows. His barrier-making Quirk is among the most defensive Quirks of all, in fact.
In battle, Hekiji can make tough energy barriers to shield himself and his allies, and at times, the Avengers could use it to give themselves a respite from enemy attacks. These barriers could also shield innocent bystanders or wounded Avengers from enemy attacks.
3 COULDN'T JOIN THE AVENGERS: Yo Hojo Is Even Weaker Than Muscular
Yu Hojo is another of the Eight Bullets, but his Quirk is not so impressive in Nick Fury's eyes. He can create hardened crystals all over his body to perform melee attacks and defend himself, and he can even form sword-like attachments with those crystals.
However, Yu Hojo can't do anything that the Hulk can't, and if Muscular cannot join the Avengers, then neither can Yu, seeing how Muscular is stronger than Yu overall. Instead, Yu will wish Hekiji well during his time with the mighty Avengers.
2 COULD JOIN THE AVENGERS: Dabi Can Perform Crowd Control
Dabi is a flame villain whose Quirk, unofficially known as Cremation, is immensely powerful. Dabi must be careful when using it, or else he will harm himself, but he can still take on most pro heroes and easily win. If he turned his life around, he could join the Avengers next.
Dabi's brutal blue flames can go everywhere and vaporize dozens or even hundreds of foes at once, and he could have wiped out entire platoons of Chitauri aliens or Ultron robots while fighting with the Avengers. He could also roast enemies such as Ronan the Accuser or Red Skull with ease.
1 COULDN'T JOIN THE AVENGERS: Spinner Can't Do Much
The gecko-like villain named Spinner has lasted quite a long time, given his limited abilities. Spinner is loyal to the League and looks up to Stain as well, to the point he often repeats Stain's ideology during battle and dresses up like him.
Spinner may be devoted, but he still has little else to offer aside from a giant sword (which was soon broken) and the ability to drive armored vans and other vehicles during car chases with heroes. Nick Fury wouldn't be impressed with Spinner.