Ultra Instinct (身み勝がっ手ての極ごく意い Migatte no Gokui, lit. "Key of Egoism") is a very rare and highly advanced mental state. It is notorious among the gods for being exceptionally difficult to master, even for them.
"You two are still thinking before you move rather than just moving. I'm afraid this habit is especially strong with you, Vegeta. This overthinking is limiting your fighting speed. Messages can only travel through your nervous system so fast. When you rely on thoughts for physical action, you lose precious fighting time. (...) Your end goal should be to master the ability to have each part of your body move independently of the other parts. But I admit this is exceedingly difficult; In fact, not even Lord Beerus has mastered it, and he's a god."
— Whis explaining Ultra Instinct to Goku and Vegeta
Toshinori Yagi (八や木ぎ俊とし典のり Yagi Toshinori?), most commonly known by his hero name, All Might (オールマイト Ōru Maito?), is the tritagonist of My Hero Academia. All Might is the former No. 1 Hero who bore the title of the world's Symbol of Peace (平和の象徴 Heiwa no Shōchō?). He teaches Foundational Hero Studies at U.A. High School.
One For All (ワン・フォー・オール Wan Fō Ōru?): Inherited from Nana Shimura, All Might's Quirk gave him access to nearly unlimited, stockpiled power. By channeling this power through his body, All Might had superhuman strength, speed, agility as well as invulnerability. All Might was so proficient with One For All that he was widely known as the world's most powerful person.