Tomura Shigaraki (Tenko Shimura) 

Shigaraki is the main villain leading the "League of Villains", where all of the villains plan together. Shigaraki, used to be called Tenko Shimura when he was a child. He loved heroes and was quirkless. But he became a villain after he got a sickness that made his appearance look very unnerving, and his desire for destruction from family trauma and manipulation by his brother, All for One. 

Shigaraki's quirk allows him to touch anything, possibly inanimate objects, and decay them (turn to dust). 

Quirk: Decay

All for One is the mentor of Shigaraki, and 2nd main villain of the series. He desires to dominate society by stealing every person's quirk, and giving quirks to other villains. After loosing to All Might, but injuring him badly, he gains a big advantage and eventually he kills the worlds greatest hero.

His quirk allows him to steal quirks from people and give quirks to people.

Quirk: All for One

Dabi is a villain with one of the most terrible backstories. His backstory is similar to Todoroki's, because he has the same father as him. His father gave him a lot of big beatdowns and treated him as a failure, because he only had a "flame" quirk. At fifteen, he broke out in flames from his quirk and could control it, and ran off into a lake to put himself out. He was in a coma for a long time and his skin got stitched and burnt, and his voice was injured. Proving he's not immune to his power, because his flames burn hotter than usual, turning blue. After, he seeks revenge for his father from his abusive behavior towards him.

Quirk: Blueflame

Stain is a side villain known as the "Hero Killer". For having very little screen time, he has quite a interesting story. Stain was an aspiring hero, but became disillusioned, and targeted heroes whom he deemed "unworthy of conviction". He believed that the only worthy hero was All Might and deemed himself All Might Worthy. Since he's not strong he resulted to use a sword that was all chipped and dull. After a fight with Midoriya and Todoroki, he broke a rib and punctured his lung. He went to the hospital and went to jail. After a long time he apears again, and gets into a fight trying to save All Might from All for One and ends up dying and loosing his quirk to him.

His quirk allows him to consume all types of blood, and depending on the type of blood it has a longer affect of stunning his opponent. Over time it wears off, as a side affect, it makes his opponent weak.

Quirk: Blood-Curdle