The My Hero Academia anime series has always been about the eternal clash of good vs evil, with caped pro heroes fighting to defend society and villains like Tomura Shigaraki striving to tear down society and rebuild it from the ground up. However, hero society was more fragile than anyone expected, and eventually, Izuku Midoriya went rogue to finish the fight on his own terms. Hero society had failed – but he could still keep fighting.
The vigilante Deku persona, or "Dark Deku," was an expression of both Deku's selfless, determined nature and the apparent failings of the pro hero industry. The Dark Deku arc made its point, but in some fans' eyes, vigilante Deku should have stuck around longer to explore these societal and personal themes in greater detail.
Vigilante Deku's Untapped Potential For Personal Growth
Vigilante Deku's very nature and existence were a comment on both Izuku Midoriya as a person and hero society as a whole in My Hero Academia. Personally, vigilante Deku represented Deku's fierce commitment to keeping all his classmates and friends safe, since Tomura Shigaraki could track him down to begin their inevitable final battle. Deku didn't want his classmates getting caught in the crossfire or being held hostage, so Deku went rogue as a vigilante to face this threat alone. However, his classmates objected, since they had come too far with Deku to just watch the final battle from a distance. They were being treated like civilians, but they were actually Deku's equals and allies. So, they fought vigilante Deku to remind him of that fact.
By then, Deku had clearly taken his classmates for granted, Quirks and all, and felt like he didn't need them any longer. Or at least, that's clearly what he felt deep down, while consciously rationalizing this as keeping his friends safe while Tomura Shigaraki hunted him down. Deku clearly didn't trust his classmates, not even powerhouses like Shoto Todoroki and Katsuki Bakugo, to help him in the final fight, and he feared for their safety to the point he insulted them. Deku was also overestimating One For All, thinking he could save the day with OFA alone.
Vigilante Deku needed his classmates and their Quirks to win, as the manga's current battle shows, and vigilante Deku was being highly immature, disregarding his classmates' strength and commitment as young heroes. He took them and One For All for granted, and only by losing to his classmates could Deku truly appreciate them and learn some humility. That indeed happened, but this arc was concluded too soon for these personal themes to be explored in full detail, and it limited Deku's personal growth. Deku's personal experience was little more than "sorry, everyone, I got carried away." A lengthier vigilante Deku arc could have forced Deku to realize that deep down, he didn't trust or respect his classmates enough to help him fight Shigaraki, and that conversation could have spoken volumes about every class 1-A student and their relationships to each other as trainee heroes and friends.
Vigilante Deku Says Something About Hero Society
The existence and nature of vigilante Deku is also a critique of the hero-centric society that Izuku Midoirya vowed to uphold and protect. Hero society is all about peace, stability, and the rule of law, but inevitably, this came at a cost that society's rejects had to pay. Quirks were not an equalizer – they made society more unequal than ever, and Quirk-based discrimination became a reality that pro heroes could never get rid of. Hero society created outcasts by necessity, and those people would, of course, seek retaliation since they have little left to lose. All this came crashing down after the final war with the Paranormal Liberation Front began, with heroes suffering massive casualties and shocking personal revelations shattering society's faith in heroes.
In this context, few heroes were able to help Deku fight Tomura Shigaraki and other high-profile villains like Muscular, so Deku adopted a loner mentality to keep himself committed to this huge burden. Normally, entire groups of beloved heroes would assemble to save the day, as they did during the Bakugo rescue operation in Season 3, but not this time. Back then, Midoriya didn't have to take it upon himself to save Bakugo with extreme force, hence no Dark Deku even with such serious personal stakes. Hero society took care of the rest, but that's over now. Pro heroes are dying, quitting, or getting injured all over Japan, and Deku can't stand seeing any more casualties from pro heroes or his classmates. Hence his Dark Deku persona, determined to embody all hero society within himself because all the other heroes and students have failed.
The My Hero Academia anime did touch on this, but with the vigilante Deku arc being so short, the full scope of hero society's failure and the increasing anarchy was not seen. It was mostly just mentioned or shown with a few brief scenes, so viewers had to fill in the gaps alone. Vigilante Deku represented Izuku Midoriya's loss of faith in his classmates and the pro hero industry alike, a bold new development in his personal arc that deserved more screen time. Vigilante Deku could have debated this with his classmates at length, which could have said much about everyone involved, but it was not to be. Yet it should have. History is being made in Japan, a dark and violent chapter in the saga of hero society, and vigilante Deku has the most to say about it – and the series should let him.