League of Villains

The League of Villains (敵連合) is a group of organized villains that is made up of both weak and powerful villains who are the main antagonists of the series. The creator of the alliance is Sensei, with Tomura being the acting leader of the alliance while Black Mist acts as the second in command of the alliance. The mission of the League of Villains is to murder All Might.

History
The size of the League of Villains is estimated to be 75 (however, after the events at the USJ, the size of the alliance is dramatically decreased due to the majority of the villains belonging to the alliance along with Noumu being captured and detained by the Police). However, after Stain's defeat and capture, many villains inspired by him (such as Himiko and Dabi) sought out the League of Villians to join it since the organization was believed to harbor Stain's ideology; thus the League of Villains has increased in numbers.

Ultimate Space & Jams Arc
The League of VIllains attacked the USJ in an attempt to kill All Might. However, the majority of the League of VIllains (except for Tomura, Black Mist and Noumu) are defeated by Class 1-A. After All Might arrives, Noumu engages All Might in battle and is defeated. Tomura and Black Mist try to finish what Noumu started but their attempt is thwarted by Izuku Midoriya and the timely arrival of the Yuuei Pro Heroes. Both Tomura and Black Mist are sucked into a Black Hole created by No. 13 (However, Black Mist creates a portal back to their hideout, teleporting themselves out of harm's way). Thus, the League of Villains is defeated and the majority of the villains of the alliance (along with Noumu) are captured and detained by the police, leaving Tomura and Black Mist as the only remnants of the League of VIllains.

Sports Festival Arc
During the Yuuei Sports Festival, Black Mist sought out the Hero Killer, Stain, due to his notoriety. Black Mist manages to find Stain and asks for a moment of his time, teleporting himself and Stain away. Stain meets with Tomura in order to test his evil. Afterwards, Black Mist teleports himself, Stain and Tomura to Hosu. While Stain goes off to finish his business, Tomura decides to humiliate the Hero Killer (as he got on his nerves) and sends three Noumus to attack Hosu. The Noumus fight the Pro Heroes and give them a hassle, as well as cause chaos and destruction along the way. By the time Izuku, Shouto and Tenya apprehend Stain, two of the three Noumus are restrained and arrested by the Pro Heroes and Police Force while the other Noumu is killed by Stain. Tomura, annoyed that nothing went his way, decides to head back to the League of Villains hideout. Black Mist and Tomura leave Hosu.

End of Term Test Arc
After Stain's defeat, the media credits the League of Villains as an organization that harbors and carries out Stain's ideology. As a result, many newcomer villains who were inspired by Stain's ideology have sought out the League of Villains in order to join it, causing the League of Villains to gain spotlight and notoriety. Two villains, Dabi and Himiko Toga, also inspired by Stain's ideology, attempt to join the League of Villains so that they can be with the organization Stain was believed to be apart of, after being scouted by a broker (who decided to take advantage of the League of Villains's new notoriety) in order to earn more money. However, the meeting between Tomura and the two potential candidates does not go well. Black Mist asks the broker to wait a few days for their reply regarding Dabi and Himiko's registration into the League of Villains.

School Trip Arc
Days after Dabi and Himiko Toga's visit to the League of Villains. Both Dabi and Himiko Toga are seen along side two others stood on top of a mountain over looking the Yuuei students camp site. When Dabi declares the Heroes will fall, he mentions it's for the sake of the future. Once all members of the squad were gathered together, they launched a surprise against the camp while declaring themselves as part of the league.

Vanguard Action Squad
A few days after Dabi and Himiko Toga's visit to the League of Villains. Both Dabi and Himiko Toga arranged for themselves and eight others to gather together for a planned attack on the students of Yuuei at their camp site located in the mountain side. Once all members of the squad were gathered together, they launched a surprise against the camp while declaring themselves as part of the league.