Shigaraki Tomura has an arrogant, twisted personality. He has been compared to a child, feeling as though the world revolves around him with little to no regard to human life, but his own. While childish he has shown a high level of intelligence, and analytical skills. He was able to deduce that All might was in fact becoming weaker. Shiagarki has also been shown to be impatient and irritable, which is shown when he attempts to kill the new members of the Villian Alliance because they annoyed him.
Due to a trauma from his childhood he would hold back his abilities and block out the memories of the event.
As time passed, he would lose allies, his master and encounter other villains to secure the position his master once held as the ruler of Japan's underworld. Upon his meeting with Kyudai Garaki he'd announce his changed goal: To destroy all of society except for what his allies want. Following this and his battle with the MLA he'd recover his lost memories and mature as a villain.
At this point Shigaraki and Black Mist make the decision to invade Yuuei High with his Villain Alliance. When he arrives he is surprised that All Might isn't there. He decides that maybe All Might if "I kill all the students?" Shigaraki is immediately attacked by Shouta, while Black Mist teleports some of the Yuuei students to different areas. Yuuei teacher Aizawa immediately attacks Shigaraki, after a brief battle he is incapacitated by Nouma. After hearing Black Mist's failure to warp all the students Shigaraki enters a state of panic. He then notices Tsuya, Mineta, and Izuku and decides to kill one of them personally to Knock down The Symbol of Peace's pride a notch". Before he can use his Quirk Aizawa cancels it out. Izuku then goes for an attack but Nouma stops it. Luckily All Might soon makes his appearance to protect his students.
Shigaraki's first quirk allows him to destroy anything upon physical contact. He must place all the fingers from his hand on the target for his quirk to activate. Upon recovering his childhood memories and awaken the true power of his decay which would aside from speeding up the rate of decay would cause all objects in contact with the decaying object to decay as well.
All For One:
The former quirk of Shigaraki's master All For One. It was duplicated with All For One holding said duplicate while Shigaraki was given the original. With this quirk Shigaraki can take and give quirks by touching someone's head with his palm. He possesses several quirks that his master had amassed. Shigaraki has used:
- Super Regeneration: Tomura possesses the ability to regenerate from any injuries at high speeds.
- Search: Tomura possesses Ragdoll's former Quirk, allowing him to view up to one hundred individuals at a time. He can see them from a distance and through obscuring barriers. This Quirk also allows him to identify their weak points.
- Air Cannon: Tomura can fire large blasts of pressurized air from the palms of his hands.
- Radio Waves: Tomura can disrupt radio waves and cause communicators to malfunction.
- Rivet Stab: Tomura creates black tendrils from his hands and his spine as an offensive technique to stab his foes.
To be able to withstand All For One, Kyudai Garaki gave Shigaraki several physical enhancements. He boasts superhuman strength, speed and durability said to rival All Might even without his Quirks.