Izuku Midoriya, also known under his hero identity Deku, is the protagonist of Kohei Horikoshi's beloved shonen anime My Hero Academia. With the dream to become the greatest Hero, Deku joined U.A High School where he trains to fulfill his ambition.
Under the guidance of All Might and bearing the power of the One for All quirk, Deku has grown extremely powerful and is already worthy of being called a splendid Hero. However, just like every other Hero in the story, Deku has faced several failures along his journey. But he doesn't let them get him down — instead, he has learned from them to become better.
7 Failing To Stop Iida
The Stain arc focused on Iida quita a lot as his brother, the hero called Ingenium, was a victim of the villain. In order to enact revenge, Iida sought out Stain despite knowing how dangerous this could have been for him.
Although everyone around Iida did try to stop him, he put himself in a dangerous situation anyway. Deku's voice, while that of a Hero, wasn't enough to reach to him through the thoughts that clouded his mind. Thankfully, Deku played a part in saving Iida later on in the story when he clashed with Stain.
6 He Couldn't Help Eri
Eri is one of the most important characters in My Hero Academia thanks to her incredible Quirk, called Rewind, which is thought to be key to several mysteries that still surround all Quirks in existence. Introduced in the Shie Hassaikai arc, Eri crossed paths with Deku and Lemillion quite early.
While both the hero students noticed something unsettling about the guy who she was with, Chisaki, they did nothing to stop him. Eri's face was covered with fear, yet Deku couldn't save her at that time. Later, both he and Mirio lamented over not being able to rescue her earlier.
5 He Couldn't Stop Mirio From Losing His Quirk
Mirio Togata was one of the key figures in My Hero Academia's Shie Hassaikai arc. Leading the fight to Chisaki's group, Mirio fought the boss all alone and did more than enough to protect Eri. However, all this came at the cost of his own powers.
While shielding Eri from the Quirk-destroying drug, Mirio's Quirk was lost. Deku, despite being close to him, wasn't able to make it in time to offer help in making Eri's rescue more efficient. In the end, Deku did defeat Chisaki using Eri's power and saved Mirio in the process as well. However, the damage was already done.
4 Failing To Save Nighteye
Just like Mirio, Nighteye was one of the main characters involved in the Shie Hassaikai arc. Being a senior figure, Nighteye played a key role in establishing the many strategies for the team's plan to work as they went to rescue Eri.
Unfortunately, in the fight against Chisaki, Nighteye reached his limit rather abruptly and ended up getting impaled by one of his Quirk reconstructions. Despite Deku being close, he wasn't able to save Nighteye from the cruel fate of death. The hero died shortly after the arc was over, but not before Deku had dealt with the threat of Chisaki.
3 Failing To Help Bakugo
Deku and Bakugo didn't have the best of relationships while growing up. The two have often been at odds with one another, and despite Deku trying his hardest to get closer to him, the feeling wasn't mutual, at least not for quite a while.
When the League of Villains' Vanguard Action Squad came to seek Bakugo, Deku was unable to keep them from taking him away. It is safe to say that Deku can't be blamed for failing to help Bakugo then, especially since his limbs were already in a bad state following the fight with Muscular. However, he still blamed himself for it. At least in Deku's own eyes, it was a failure on his part..
2 He Couldn't Help Shigaraki
Shigaraki Tomura is the leader of the Paranormal Liberation Front and the most powerful villain in My Hero Academia right now. While he is evil currently, that wasn't always the case. As a child, Shigaraki, then known by his real name Tenko, wanted to be a Hero. Sadly, the helping hand that once reached out to Deku never arrived for him.
Being consumed by everything, Shigaraki ended up becoming a Villain. However, Deku still senses the real Tenko within him. When the two fought in the Liberation War arc, Deku mentioned that he felt Shigaraki needed saving. However, he was unable to save him from the clutches of All For One, and the villain only sank deeper.
1 Taking Everything On His Shoulders
Following the Paranormal Liberation War arc, the knowledge of Deku being All Might's successor was eventually revealed to quite a lot of people, and the secret was out. Consequently, Deku had to leave U.A and he ended up working separately for quite some time.
While Deku didn't do a bad job, he was too hard on himself during this time. This was evident from how his friend conversed with him when they met. For someone who aimed to become the next All Might, this was nothing less than failure, as All Might always saved people with the brightest smile on his face. Thankfully, it didn't take long for Deku to receive help. Soon, he returned to being the Hero that the fans have known and loved over the years.