All Might (Toshinori Yagi)

One For All (ワン・フォー・オール, Wan Fō Ōru?): Transferred to him from Nana Shimura, Toshinori's Quirk allowed him to stockpile an enormous amount of raw power, significantly enhancing all of his physical abilities to a superhuman level, resulting in unbelievable feats of strength, speed, agility, and durability. Unlike other known users of this Quirk, Toshinori was noted to have an innate instinct for wielding it, mastering it almost instantly with no aid from his teachers. Also, seemingly unique to him, Toshinori's mastery of this Quirk enabled him to morph himself into a towering, powerfully built man to hide his identity from society.

All Might was so proficient with One For All that he was widely known as the world's most powerful person. During the peak of his abilities, he's been shown to deal with many threats at once in mere seconds effortlessly. Even more, after being grievously injured by All For One and transferring One For All to Izuku, All Might, using only residual "embers" of his former Quirk, could still achieve tremendous feats well-above everyone else (besides All For One).

Unwavering Optimism & Altruism: He lives to save others and maintains a bright, cheerful, and encouraging demeanor to reassure the public and his students.

The "Symbol" Mentality: He acts as a pillar of hope, using his fame to deter crime, often characterized by his catchphrase, "I am here!".

Fatherly Mentor: He cares deeply for his students, especially Izuku Midoriya, showing intense rage when they are endangered and pride in their growth.

Dedicated and Principled: Despite his injuries and declining strength, his commitment to justice is absolute, driving him to keep fighting even when physically depleted.

Behind the Smile: While outwardly boisterous, he is actually quite reserved, planning, and at times doubts his own ability to live up to the impossible standards he has set.

Action-Oriented: He prefers direct, often simple, solutions to problems, relying on his overwhelming power, yet he is dedicated to training the next generation to succeed him. 

All Might's hero persona appears to be derived from comic book superhero stereotypes: exuberant and filled with dramatic flair. He always protects and saves innocent people with a huge smile. The habit of smiling was ingrained in him by his mentor, Nana Shimura, who believed that the ones who smile are the ones who are the strongest. Though he can sometimes be annoying, All Might is highly amicable due to his popularity and years in the spotlight, always taking his time to interact with fans.

Once All Might reverts to his true form, he becomes reserved and solemn, avoiding attention in direct contrast to the grandiosity of his hero identity. While he's an optimist, he still ensures his goals are grounded in reality. When a Quirkless Izuku tells him about his goal of becoming a hero, All Might commends him for having a dream but reminds him to stay realistic and suggests he enter another profession that helps people. He considered the harsh words necessary to save the boy from long-term frustration. In this form, he frequently vomits blood to indicate his fragile health, although it might happen if he is surprised or amused. Regardless of which form All Might is currently taking, two personality traits always present in him are his optimism and oafishness.After his fight against All For One, he considered it necessary to keep his weakened state hidden from the public for the sake of keeping up morale. Unfortunately for All Might, injuries inflicted on his body were starting to take a toll on him. Despite the concern and warnings from some of his close associates, All Might's determination to preserve society from evil prevented him from relinquishing his role as the Symbol of Peace. His smile, a gesture that served to calm others, started becoming more of a way for All Might to hide his fears and insecurities from the general population.