The following article discusses events from Season 6 of My Hero Academia, currently streaming on Crunchyroll. Under the guise of being a respectable doctor and generous philanthropist named Dr. Kyudai Garaki, this dangerous scientist managed to continue with his outlandish experimentations in secret for several years. Society initially ridiculed him for his radical beliefs in the Quirk Singularity Theory, which lead him straight into All For One's open arms, ripe and ready for manipulation.
With no one besides a power-hungry madman to supervise Dr. Ujiko, he was left to his own devices and has subsequently become one of the League of Villain's most valuable assets, as the mastermind behind the potent Nomu forces. If people had accepted his genius intellect all those years ago, and Dr. Ujiko could have used his knowledge for good, what might the world look like today?
The Quirk Specialist
The concept behind the potential Quirk Singularity problems is based on more than just a demented doomsday conspiracy theory and may very well have some scientific validity behind it. Eri is the perfect example of what could happen if a youngster inherits a combination of powers that simply overwhelms them, leaving the child incapable of controlling their abilities, with potentially disastrous results. Many unfortunate souls have also been burdened by the formidable strength of their Quirks, while most have been labeled as evil and essentially forced onto a villainous path (such as Himiko, Bubaigawara, and Gentle Criminal, among others).
Taking ownership of a Quirk is not always sunshine and daisies, as numerous superhuman abilities have some kind of drawback to balance things out slightly. This 'handicap' often compels the user to be more careful with their powers, as the consequences of their action come straight back to bite them in the rear. For example, Denki's incredible Electrification causes him to temporarily lose touch with his brain cells; while Yuga Aoyama and Ochaco agonize over intense stomach cramps if their Quirks are overused; and Deku has to cope with the near-fatal toll that One For All takes on his body.
Individuals such as Power Loader and Mei Hatsume have dedicated their lives to creating specialized Hero equipment, which often assists the human body in handling their Quirks better (such as with Deku's gloves and Ida's boots). But even they have their limitations. If anyone has proven to have the most thorough understanding of the biological components of humanity's relationship with Meta Abilities, it is Dr. Ujiko. While his procedures may be painful and unorthodox, the spectacular results are undeniable (just ask Shigaraki for a review.)
The Doctor Is In
The wicked young prodigy may not have been able to utilize All For One as efficiently as he has done, if not for the extra buffering to his genetic structure supplied by Dr. Ujiko. So far, the ability to wield multiple Quirks at once only applies to a select few, and, as can be seen with All For One and the undead Nomus, trying to contain so much power can certainly have an adverse effect on the body. Fortunately for them, Dr. Ujiko is always ready and waiting to improve their quality of life somehow, essentially producing an advanced race of superhumans in the process.
If Dr. Ujiko had spent his energy helping the good guys instead, or everyone in general, Japan would probably not be as chaotic as it is today. As is seen with Deku, the "good" doctor is responsible for assessing youngsters' Quirks (or lack thereof), meaning that he could easily weed out troublesome powers from as young as four-years-old. He could then guide the child (and parents) toward a safer solution to adjusting to their Quirks, which may include augmenting the child's DNA to nullify, or at least reduce, the negative side effects, allowing them to perform to the best of their ability.
A Helping Hand
Although the scientist utilizes All For One's Quirk for his experiments when necessary, he mentions that he is able to manipulate Quirks without his master's assistance, it simply takes longer. He could therefore work independently if he so chooses, realigning his mission with more positive goals. For cases such as Endeavor's overheating issues, Dr. Ujiko could supply the Hero with a cooling Quirk to counter the issues (and essentially apply the reverse to assist Bakugo's inability to cope with the cold.) He could find a way to Earth Denki's extra charge, redirecting the electric field away from his head, and would likely know just what to do with Eri's unfortunate situation.
For people such as Eraser Head or Kyoka Jiro, who have amazing abilities but not much offensive power, Dr. Ujiko could help them kick things up a notch by offering them some new gifts; imagine how potent Aizawa could be with Blackwhip in his arsenal instead of his binding cloths! Jiro could become equally as potent if she shared Kenji Kushida's Absorb Sound ability, which could likely be used in conjunction with Earphone Jack to create a super-charged sonic attack. If little Tsuyu Asui became a supersized frog with Mount Lady's Gigantification, she would also pose a much greater threat on the battlefield; and the same could be said for Minoru Mineta.
All For One's Greatest Ally
All For One is a one-man army without any help, but his life has evidently improved with Dr. Ujiko by his side, while Shigaraki certainly wouldn't be half the man he is today without the old man's help. Team Endeavor specifically targets Dr. Garaki at the beginning of the Paranormal Liberation War because the Heroes realize that without him, the League of Villains would lose an essential cog in their system.
The miscreants already showed great strain when their supply of Nomus is cut off for a while, causing their reputations to suffer and causing a slight panic (particularly from Shigaraki, who came to rely on his gargantuan toys.) Not only would Good Guy Dr. Ujiko be extensively beneficial to society in general, but simply removing him from the villains' clutches is already a huge game-changer. Although, whether the Heroes can keep Dr. Ujiko in their custody, particularly with an Awakened Shigaraki on the loose, is a whole other story.