Midoriya Izuku has been consistently using more of One For All's power than fans are used to seeing ever since My Hero Academia Season 6 started. His most recent achievement may be the most astounding of all: when he faced Muscular, a bad guy who could have been defeated by One For All at 100%, Deku easily defeated him in a single move. His power surge is unmatched and significantly more dramatic than anything he has accomplished up to this point in his quest to become a hero. Here's how Deku quickly became so powerful.
Deku is More Linked to One For All Than Ever
Deku has been granted access to even more of the previous owners' abilities after communing with them in the vestige realm and is set to unlock the final few Quirks in the near future. Deku's most recent Quirk is En's Smokescreen, and the original wielder is instructing him on how to use it most effectively. Deku's meeting with One For All's previous wielders has resulted in him being more attuned to the Quirk than ever before, allowing him to freely communicate with their remnants even in the heat of battle. They can share their experiences and opinions with Deku, seemingly with no trouble at all, like a perpetual Quirk Avatar state.
After decades of being enmeshed with One For All, the various Quirks Deku has access to now have been strengthened by their proximity to the Quirk. They are much more powerful now than they were in their wielder’s original lifetimes but are still ultimately support-type Quirks. Deku himself has undergone a gradual strengthening process throughout the entire series. His strict training regimens have allowed his body to withstand the consistent use of Full Cowling at 30% of One For All’s capacity. Using the principle behind his Air Force super move, he is able to surpass this limit by raising the percentage of One For All to 45% right at the moment of his blow’s impact, maximizing the damage and minimizing the risk of injury.
Deku's arsenal of support items has grown to match the expanding capabilities of his still-developing Quirk. He's wearing an improved version of the compression support item Mid-Gauntlets from My Hero Academia: Two Heroes. This version strengthens his entire body rather than just one arm, allowing him to use more of One For All's power without injuring himself. Nonetheless, they are still prototypes for a future product. Melissa Shield's finished support tool will provide him with even more protection.
Years of Hero Training Have Finally Paid Off for Deku
Before Deku even had a Quirk, he was studying the movie sets of Pro-Heroes he admired and attempting to mimic their effects. Years of this behavior have given him an intrinsic understanding of how to realize a Quirk’s full potential. He’s making the most of several new abilities, picking and choosing the perfect counter to whatever new danger he runs into on his vigilante crusade. He’s only unlocked these Quirks for a short while but is already handling them with the finesse of a seasoned Pro.
Of course, this many Quirks would have been impossible to manage if Deku hadn’t trained to handle multiple processes at once with Endeavor. During his work study at Endeavor agency, Deku spent his time learning to handle multiple Quirks from the Number 1 Hero. Endeavor introduced him to a concept known as parallel processes, constantly training his mind to shift from one Quirk to another as needed, until it became an instinctive process to him. During his match with Muscular, Deku put his mastery of this principle on display, activating one Quirk after the other smoothly and without any negative repercussions on himself. By combining all the tools and lessons he’s experienced so far, Deku is now a one-man vigilante world preventing My Hero Academia’s Hero society from slipping further into chaos.