Mirio Togata is among the strongest heroes in the My Hero Academia series, given his unique Quirk.
With the use of Permeation, he can phase through objects like it was nothing. Mirio trained very hard to use this extremely difficult Transformation Quirk. As part of his efforts, this U.A. high schooler became a member of the Big Three. He was even a strong contender to surpass All Might.
With that said, Mirio is not invincible by any means. There are a handful of characters that would give him a very hard time in My Hero Academia. It all depends on certain factors in the match.
My Hero Academia characters that Mirio can beat
4) Eijiro Kirishima
For all intents and purposes, Kirishima should be a natural counter for Mirio. The Class 1-A student can use Hardening to enhance his durability. His body also has jagged edges, which means his opponents can easily cut themselves.
With that said, Mirio does have a significant advantage with his speed. He can also avoid every single attack from Kirishima. During the Shie Hassaikai arc, Mirio completely blindsided Class 1-A in a matter of seconds.
Kirishima will be caught off guard if Mirio resorts to his powerful special move, the Phantom Menace. He might not even activate his Quirk in time.
3) Chizome Akaguro - Stain
Stain is just as fast as Mirio, yet he is better suited for close range combat. Mirio would have to avoid those cutting-edge knives and swords.
While being a brawler should put him at a disadvantage, he can still phase through Stain's attacks. Mirio would have to avoid getting cut, since he would be paralyzed if the villain licks his blood. While having a blood type O means it won't last too long, Stain only needs a second to kill someone.
Ultimately, Mirio will have to rely on a combination of speed and skill for this battle. It would be tough, but he could pull it off in My Hero Academia.
2) Shota Aizawa - Eraserhead
Aizawa has a very rare ability to shut off Quirks in My Hero Academia. Mirio will have to mainly rely on his fighting skills here. Aizawa can be tricky to deal with, given his proficient use of capturing tape.
With that said, Mirio's body is in peak conditioning. He does have the natural reflexes to dodge Aizawa's attacks. More importantly, Aizawa cannot keep his eyes open forever. The moment he blinks, he will reset his Erasure ability.
By that point, Mirio can phase through the floor and launch a counterattack. This will be a very close match in My Hero Academia. With that said, Mirio is much younger and doesn't have the list of injuries that Aizawa has.
1) Kai Chisaki - Overhaul
My Hero Academia would be a lot different if Mirio didn't lose his Quirk in the Shie Hassaikai arc. He was dominating his fight against the Yakuza boss. Mirio even put up a great fight without his Quirk, which says a lot in My Hero Academia.
Overhaul has a dangerous ability where he can restructure anything he touches. For example, entire floors can turn into hazardous spikes. Overhaul can also destroy his enemies by disassembling them.
Of course, if he cannot touch his opponents, then it's all fair game. Permeation is a direct counter to Overhaul's powerful Quirk. Mirio can simply phase through every single attack. With speed on his side, the hero can definitely outlast the villain. Overhaul is clearly outclassed in a physical confrontation.
My Hero Academia characters that Mirio cannot beat
4) Rikiya Yotsubashi - Re-Destro
My Hero Academia databooks suggest that Re-Destro's stats are completely maxed out. This makes perfect sense, given that he can directly fight Shigaraki without the fear of getting hit. Mirio isn't going to combo attack Re-Destro like he did with Overhaul.
The biggest problem Mirio faces is when Re-Destro turns himself giant, via his Stress Quirk. Even with only an 80% output, the villain becomes a massive beast. Mirio has far too much surface area to cover with simple punches.
What doesn't help is that Re-Destro can destroy the ground below him, so the hero doesn't have many hiding places. Mirio can dodge most attacks, but Re-Destro is even faster than he is. He is put in a terrible position here.
3) Enji Todoroki - Endeavor
Mirio relies on his brawling style, which is effective against most characters in My Hero Academia. However, it won't be against a literally fired-up Endeavor.
All the Pro Hero needs to do is cover his entire body in flames. Mirio won't be able to land a single punch without burning himself badly. Phasing through matter doesn't mean anything if he can't attack the Pro Hero.
Endeavor would also have to hold back just so he wouldn't kill the U.A. student. His flames can spread through large distances, leaving Mirio with very little room to move around freely.
2) Izuku Midoriya - Deku
By this point in My Hero Academia, Deku has finally surpassed Mirio. His physical stats are much higher than they were in the Shie Hassaikai arc. With his mastery of the OFA Quirk, Deku can dish out some real damage.
Mirio can be really difficult to hit. With that said, Deku is very good at figuring out battle tactics. He is among the smartest Class 1-A students, after all. Deku just needs to carefully time his attacks. All it takes is a single 100% Smash technique to finish the job in My Hero Academia.
Keep in mind that Deku can also use multiple Quirks for various purposes. His fighting style is far more versatile than Mirio's.
1) Tomura Shigaraki
Shigaraki is very similar to Overhaul, in the sense that both villains are deadly in close range combat. However, the former has evolved far beyond the latter in My Hero Academia. Shigaraki has finally awakened his true abilities.
If Mirio was fighting Shigaraki before the Meta Liberation Army story, then he would likely prevail. However, the latter can now decay entire landscapes within the blink of an eye. Decay now spreads itself through a chain reaction, meaning that Shigaraki doesn't even have to physically touch Mirio.
The hero would put up a great fight against the most dangerous villain in My Hero Academia. However, Shigaraki's reach is far too great for Mirio. There are too many instances where he can get decayed.
Note: This article reflects the writer's personal views.