In a series such as My Hero Academia where there will always be heroes to fight and repel villains and other forces of evil, it is only inevitable that there is going to be plenty of suspense and tension, in order to properly sell the threat that the antagonists pose.
However, instead of the generic superheroes powering up to overcome the bad guys, this isn't always the case, with there often being a real sense and feeling of dread that something might go wrong and the good guys may well lose badly. While the majority of such moments in My Hero Academia center around the likes of Tomura Shigaraki and Kai Chisaki, or Overhaul, as their general demeanor and personalities are generally creepy and unhinged, the moments when they interact or threaten our heroes' safety are arguably when they are at their scariest and most despicable.
10 The Reveal Of Stain's Quirk Made His Fight Against The Students Even More Sinister
The Hero Killer Stain was one of the most interesting villainous characters in My Hero Academia, especially outside of the main circle within the League of Villains. Although he had already been introduced by the time that he was confronted by Tenya Iida, the subsequent faceoff is what really showcased him and why he was so feared.
The moment when his Bloodcurdle Quirk was teased and then explained was not only shocking, but also befitting of his terrifying demeanor.
9 The Sludge Villain Engulfing Izuku Was A Horrifying Sight
The villain that sparked Izuku Midoriya and All Might's friendship and mentorship was the Sludge Villain that appeared in the anime's first two episodes. It started by viciously attacking the poor defenseless and Quirk-less Izuku, subsequently taking over his body in a truly terrifying sequence, instantly setting the tone for the show's villains.
Although it would later take control of Bakugo in a similar way, the horrific and sinister way that it burst onto the scene and attacked Izuku was both scary and shocking. It was the first of many such moments to occur over the course of My Hero Academia.
8 Aizawa & Thirteen Suffering Huge Defeats To The League Of Villains Was A Shocking Introduction For The Group
My Hero Academia's Episode 11 sees the battle against the League of Villains near its climax with the evil organization already having made its dramatic entrance. The episode contains genuinely scary moments, from Eraser Heard, Aizawa, being broken down and crushed by Tomura Shigaraki and the enhanced Nomu, to Kurogiri outsmarting and seemingly killing Thirteen.
Shigaraki even looks set to use his Decay Quirk on a helpless Asui, only for Eraser Head to erase it at the last second, saving her life. While the initial reveal of Shigaraki with his rather terrifying design and demeanor was scary in itself, the first of the League of Villains' cruel acts and their attacks on the students and teachers really upped the show's intensity.
7 Gigantomachia's Debut Presented A Horrifying New Villain
"Smoldering Flames" sees the fallout from the Shie Hassaikai arc and the transition onto the next adventures, with the main reveal being that of Gigantomachia. When Gran Torino and Detective Tsukauchi finally catch up to and apprehend Kurogiri from the League of Villains, the Warp Gate user reveals that All For One has another valued project other than just Tomura Shigaraki, the colossal Gigantomachia.
Gigantomachia's reveal not only shakes the ground but it shakes everyone in attendance, due to the sheer power and menacing aura of the beast. Looking like something out of Attack on Titan, Gigantomachia certainly appeared to be a gamechanger in the ongoing battle between heroes and villains.
6 Muscular's Murderous Intent Made Him A Formidable Opponent For Deku To Overcome
The episode "My Hero" sees the start of the assault by the League of Villains on the Forest Training Camp, with the heroes and students becoming separated into smaller groups in the face of peril. Not only are the likes of Aizawa ambushed and seemingly put out of action, but Kota, the child that Izuku had been trying to bond with, is all alone and cornered by one of the villains.
This villain, Goto Imasuji, who also goes by Muscular, is not only willing to attack a child but is also revealed to be the one who murdered Kota's parents a long time ago. With an already tense situation, the fact that Deku arrives to fight him one-on-one only for his villainous powers to be properly revealed in all their glory makes for a terrifying and intense exchange.
5 Deku & Lemillion's Encounter With Eri & Overhaul Was Tension At Its Highest
Izuku Midoriya and Mirio Togata came face to face with Kai Chisaki, the intimidating Yakuza leader of the Shie Hassaikai, and witnessed his intriguing and concerning relationship with a little girl named Eri. The meeting was a scary moment as viewers already knew about him, even if Midoriya and Togata only knew about him from Nighteye.
Eri subtly gripping Deku's arm and asking him to help her made for an emotional and morally conflicting scenario, with the two heroes knowing that they should do something, but ultimately they had to refrain from doing so, due to Overhaul's apparent murderous intent.
4 Stain's Crazed State After His Supposed Defeat Was Hauntingly Impactful
In "Climax," even after the Hero Killer Stain had been apprehended by Izuku Midoriya, Tenya Iida, and Shoto Todoroki, he still found a way to break free and deliver one of the most sinister moments of the entire anime.
His demeanor changed somewhat to a crazed and zombie-like state, muttering about only letting All Might kill him, all the while letting off an aura that caused everyone else to freeze, even the likes of Gran Torino and Endeavor. With the terrifying backdrop of a blood-red moon and his crazed approach towards the heroes, it was all stopped by him succumbing to his injuries and losing consciousness while still standing up.
3 Tomura Shigaraki Ambushing & Threatening Izuku While Shopping Was An Intense Moment
In "Encounter" at the end of the second season, Tomura Shigaraki, the League of Villains' immediate leader brazenly confronts Izuku Midoriya in the middle of a shopping mall for a nice "chat," while everyone else unwittingly goes about their days.
Initially posing as a fan, Shigaraki quickly gets his hand around Midoriya's neck so as to encourage him not to do anything reckless. Towards the end of this threatening discussion, Ochaco Uraraka stumbles across them, quickly realizing that something isn't right, prompting Shigaraki to leave. The whole situation, from the creepy music to the scary animation, really ramped up the tension and made this one of the most terrifying moments that didn't involve an all-out fight.
2 The Introduction Of Moonfish In Action Was One Of The Anime's Most Disturbing Debuts
In an anime about heroes, it is only natural that there are countless villains introduced for them to fight. While they are often introduced and presented in evil and sinister ways, there are very few introductions as sinister and terrifying as that of Moonfish, during the Forest Training Camp arc.
Moonfish is introduced hunched over the severed hand of UA Class 1-A member Mezo Shoji, immediately displaying his bloodlust with his terrifying moaning and general demeanor. This immediately puts across his Blade-Tooth Quirk as a formidable and terrifying obstacle that the students must overcome.
1 All For One's Arrival Destroyed Best Jeanist & Turned the Kamino Incident's Tide
All For One finally revealing himself in My Hero Academia's third season was both shocking and impactful as it was the turning point in the Kamino incident, when all seemed to be going well for the heroes.
The suspenseful music as he arrived on the scene and decimated Best Jeanist in brutal fashion, all while Izuku and the others who had come to rescue Bakugo watched on in horror. Coinciding with the other villains escaping from the likes of All Might at the same time, this stacked the odds against the heroes in a horrifying turn of events.