[Answer] How did All Might get injured in One Piece | You can’t miss

How did  All Might get injured? "I want to be a pillar for justice that people can trust." Toshinori Yamagi was born Quirkless in a world when evil reigned supreme due to All For One. Because there was no hero to trust, crime rates were rising. The boy was inspired to be a powerful hero, who could offer hope to innocents and defeat evil. 

All For One severely injured All Might in their first battle

1. How did All Might get injured?

All For One severely injured All Might in their first battle. Toshinori Yamagi became the first OFA user ever to defeat All For One sometime in the past. Both were severely injured during this fight.

All Might lost most of his respiratory system. This would mark a historic turning point in My Hero Academia. All Might's slimming down is due to multiple surgeries and side effects. His eyes also looked very sunken due to constant stress.

All Might took his Pro Hero role very seriously. This also meant that he could not use his OFA Quirk. Although he could temporarily transform into his muscular form for a short time, he was unable to do so. All Might was short on time so he had to find a replacement. It was a Quirkless boy, Izuku Midoriya also known as Deku.

2. The Origin of All Might

Toshinori met Nana Shimura, a Pro Hero in his teenage years. He shared his ideas with her. Nana was told by Toshinori that he wanted to see a world where everyone could smile and live together happily. To make that happen, the world required a "Symbol for Peace" to instill a new age harmony. Toshinori believed that he could be the pillar of inspiration for all people. Nana believed in the Quirkless boy, and she took him on as her apprentice. Toshinori was trained by Nana and One For All was passed to him. He became the eighth torchbear of the great power. Toshinori would continue to hold the power for forty more years. 

Toshinori went to U.A. Nana's friend Gran Torino was Toshinori's homeroom teacher. Toshinori was strong enough to use One For All at 100% right from the beginning of training. Gran Torino focused mainly on teaching Toshinori how fight properly, even though his training methods were so harsh, he accidentally instilled fear in him. 

All Might Rising

3. All Might Rising

Gran Torino takes All Might to his master and flies him away. The danger of facing All For One is one of the consequences of inheriting One For All. Gran Torino, Nana and Toshinori faced All For One eventually, but the villain was too strong. Nana gave her life so Toshinori could continue to live, and entrusted his safety to Gran Torino. Toshinori was unable to watch his master give up her life for All For One's greatest evil.

Gran Torino made a promise to Nana that he would continue training Toshinori. Toshinori was devastated by the loss of his master and could not train to his full potential. Toshinori was plagued by thoughts of revenge and wanted to exact justice on Nana, whom he considered a true hero. 

Gran Torino reminded Toshinori of his enemy, a man who has walked the earth over 100 years. Toshinori wept as Gran Torino reminded him that his master had given up all to raise One For All's next torchbearer. He also admitted that he considered her his mother. Gran Torino tells All Might that they can cross the ocean.

Gran Torino advised him to go to the United States to get experience as a hero after he graduated. Toshinori was reminded by Gran Torino why Nana had given up her life and he regained his determination. Toshinori received his degree from U.A. that spring. 

Toshinori was ready to cross the ocean. Toshinori recalled his master's signature smile before he left. Toshinori shaped his hair, and donned his signature smile for All Might. 

Thus, we have just provided you with some information about how did  All Might get injured. Hopefully this article will help you better understand the character  All Might and the sword he uses.
 

Source: 9Anime