Villains

A Villain is a person who commits crime and in the process put innocent lives at stake. There are all different types of villains in this world.

History
Villains started as a group of people who wanted to use their new gifts to benefit themselves instead of helping others. Unlike Heroes, these people wanted to use their Quirks to commit crime and evil. According to Naomasa Tsuchauchi, in the current age, the crime rate committed by Villains is quite low as a result of being pressurized by the huge amount of Heroes.

A villains' group called the League of Villains led by Tomura Shigaraki attacked the USJ in an attempt to kill All Might after infiltrating Yuuei and learning of All Might's whereabouts. 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 harms 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.

During Yuuei's Sports Festival, the notorious villain called Stain heavily injured Turbo Hero Ingenium, leaving him for dead. Afterwards on a rooftop, Black Mist of the League of Villains asks Stain for a moment of his time and teleports him to the League of Villains hideout.

At the League of Villains hideout, Tomura invites Stain to join the League of Villains as his notoriety would benefit them greatly. Tomura also tells Stain what their goals are. However, Stain is not amused with Tomura's child-like attitude as well as his goals and begins arguing with him. The mysterious voice on the monitor asks Black Mist to let Tomura and Stain continue with their meeting as Tomura's meeting with Stain (an experienced infamous villain) will stimulate Tomura's growth.