The following contains spoilers for My Hero Academia Season 6.
Since the world of My Hero Academia is ruled by superpowers referred to as Quirks, those with powerful abilities are naturally on top. But for the young Midoriya Izuko, who was born without a Quirk, living in such a world was painstakingly difficult, especially since his dream was to become the No. 1 hero. However, his life changed when his idol All Might passed his Quirk to him, allowing him to bring out an immense amount of strength. But in order to wield such power, Midoriya had to undergo numerous training regimens, honing both his body and mind.
Midoriya had gone through a lot in My Hero Academia, but his efforts did pay off. He ranked high in his class and became a dependable hero. But with the series' main antagonist hot on his trail, Deku still couldn't catch his breath. He had to get stronger at an unbelievably fast pace if he hoped to stand on Shigaraki's level. And in his attempt to do that, Dark Deku was born. This new persona exponentially boosted his ability, while also honing his mastery over his numerous Quirks. This raises the question: how strong is Dark Deku?
Who Is Dark Deku?
Izuku Midoriya undeniably embodies what it means to be a hero. He possesses a heart that does not allow him to abandon anybody, while at the same time willing to offer himself for the sake of others. But this same trait is what gave rise to the birth of Dark Deku. Contrary to what the name suggests, Dark Deku isn't necessarily evil. He remains to be a hero and a highly efficient one as that. The only difference between the normal Deku and Dark Deku is that Dark Deku operates in isolation. He does heroics like a shadow, coming and going like a thief in the night.
In order to understand how such a persona came to light, a brief rundown of Deku's relationship with Shigaraki and All For One is imperative. Having inherited One For All from All Might, Midoriya held the key to standing up and defeating Shigaraki and All For One. The villains, of course, weren't going to let Izuku garner the power-ups he needed to oppose them. After escaping the depths of Tartarus, All For One immediately hunted down the young hero. He constantly tracked his every movement, sending a number of notorious villains to take down and capture Deku. It's exactly because of this that Midoriya chose to roam the streets in isolation, sparing the people close to him from the danger that is All For One. In addition, All For One's threat forced Izuku to step up his game.
During his stint as Dark Deku, Midoriya roamed the street in search of crime. While doing this, he mastered a number of his Quirks with the guidance of the previous One For All users. While arguably efficient, Dark Deku was short-lived. His Class 1-A classmates eventually stepped in to stop his vigilantism. They combined their forces to stop Midoriya and bring him back to U.A. for a much-needed rest.
How Strong Is Dark Deku?
Midoriya's time as Dark Deku may have been short, but it is during that time that he truly tapped into One For All's potential. He was highly efficient as Dark Deku, minimizing unnecessary movements and utilizing multiple Quirks simultaneously. Unlike All Might who only utilized super strength at its maximum potential, Dark Deku harnessed the power of the other OFA wielders. Danger Sense was almost always activated, while also maximizing the use of Blackwhip, Smokescreen, and Float. In addition to that, he also made use of One For All's supernatural strength capabilities, adjusting his strength level to the absolute minimum required to accomplish a task – Dark Deku was a formidable combat force.
In his attempt to capture Midoriya, All For One sent out a number of notable villains. Dark Deku once again faced off with Muscular, who was one of the Tartarus escapees. This time around, however, Dark Deku didn't have much difficulty defeating the villain. Dark Deku also defeated the infamous Lady Nagant, though with some difficulty. But most notable of all, Dark Deku almost snags a win over the combined forces of Class 1-A. In fact, he would have won if it wasn't for the fact that he was already over-fatigued at the time of their confrontation.
With his heroic feats and fighting ability, Dark Deku certainly reached Hawks and Best Jeanist's level at their prime. Thoughm he still had a ways to go before becoming the No. 1 hero, as Dark Deku fell short of unleashing Midoriya's full potential and also came with a very steep price.
Dark Deku Has A Great And Obvious Flaw
While Midoriya's growth during his Dark Deku phase was undeniable, it didn't go without consequences. Midoriya was constantly running at full power while patrolling the streets as Dark Deku, he did this to prevent as many casualties as possible. By doing this, he quickly mastered his numerous Quirks and honed his fighting abilities. His consecutive victories were proof of how far he had gotten from this constant training and running around.
This put Midoriya in an extremely fatigued state where he literally didn't have any room to breathe at times and could he barely stand once he stopped moving – which proved to be detrimental to his physical and mental state. This was evident when his body almost gave out, nearly allowing a hated villain to escape. If his classmates hadn't arrived in time, Deku might have been in trouble. His classmates defeating him ultimately gave him the break and rest that he needed. And while it marked the end of Dark Deku, it was one huge step for Midoriya's power-up, especially as his fight against My Hero Academia's worst villain drew near.