My Hero Academia's third season may be over, but it's set a lot of things in place for the future. Now that the top student in U.A. High School, Mirio Togata, has been introduced, Midoriya learned just how hard he'll need to work in order to succeed.
Mirio demonstrated his "powerful" quirk by taking out the entirety of Class 1-A while his permeation abilities left him nude and in charge.
When the battle began, Mirio took Class 1-A by surprise when his clothes fell off of his body. After this, he seemingly warped around the entire class and punched each of them in the stomach. Shouting "Power!" Mirio overcame them quite easily, but Midoriya realized that he must have been making calculated movements rather than pure warping.
Midoriya nearly got him, but he phased through Mirio completely and Mirio was able to deal a knockout blow to Midoriya with his ultimate move. It turns out rather than just phasing through matter and "warping," Mirio's quirk is permeation. By activating his quirk, his body can go through anything, including the ground. If he releases his quirk when in the ground, he gets repelled because two pieces of matter cannot occupy the same space. He alters the angle of his trajectory when he gets repelled, resulting in his "warps."
The more impressive thing is that Mirio says his quirk isn't powerful at all, despite the examples otherwise. When it's activated, he can't breathe, see, hear or feel anything as all matter just passes through. So in order to phase through things, Mirio has to concentrate on activating single parts of his body and de-activating them at certain times.
Thus Mirio eventually fell to the bottom of the class, but trained his body and quirk with experience in order to get his fighting style as effective as it is now. So his quirk may seem powerful, but it's really just an example of the kind of hard work Midoriya and the others will need to put in to make the most of their quirks as well. It's definitely a good example for the others that this is the work effort of the school's top student.
My Hero Academia was created by Kohei Horikoshi and has been running in Shueisha's Weekly Shonen Jump since July 2014. The story follows Izuku Midoriya, who lives in a world where everyone has super powers, even though he was born without them. Dreaming to become a superhero anyway, he's eventually scouted by the world's best hero All Might and enrolls in a school for professional heroes. The series has been collected into 19 volumes so far, and has been licensed by Viz Media for an English language release since 2015.