Although My Hero Academia is centered around the abstract concept of justice, protagonist Izuku Midoriya manifests every stereotypical aspect of heroism into reality. Deku has been a hero since he was a small child, even after learning that he doesn't have a Quirk.
Obtaining One For All from his hero-turned-mentor All Might does nothing to change his original perception of fairness and equality, but it does gives him the power and opportunity to bring about real change. In fact, there are very few occasions when Deku's behavior can be considered un-heroic, or neutral. He is almost always the first person to offer assistance to those in need.
Manga Spoilers Below
10 Deku Rushes To Help Bakugo Out Of A Stream
Deku is devastated when he learns of his Quirklessness at a very young age, but the revelation does not put a damper on his heroic spirit whatsoever. When his dear Kacchan slips off a bridge and lands in a stream, Deku rushes to help him out, offering genuine words of comfort.
Unfortunately, Bakugo takes his friend's kindness as hubris because he truly believes that people without Quirks are inferior to him. Deku doesn't take the rejection to heart, though.
9 He Points Out Kai Chisaki's Hypocrisy
Deku encounters Overhaul with Lady Nagant. The former is completely powerless at this point, having lost his arms to Tomura Shigaraki. The young hero avoids his opponent's projectiles and "rescues" Overhaul in the process, an act of self-sacrifice that confuses (and impresses) Lady Nagant.
However, Deku doesn't hold back his anger when Overhaul whines about being unable to beg his Boss for forgiveness. Deku calls him out immediately, asserting that Eri deserves those apologies more than anyone else.
8 Deku Declares That He Will Save Tenko Shimura
The previous wielders of One For All and Deku discuss the options available to them, with a major one being Tomura's fate. Nana Shimura flat-out demands to know if there's anything that would prevent Deku from ending Tomura's life, implying that she's completely fine with her grandson being killed.
Deku mulls the idea over in his mind but inevitably informs the others that he intends to save Tenko from All For One's clutches, thereby passing the secret test that Nana had set for him.
7 He Meddles In Other People's Lives
Deku insists on inserting himself in between conflicting parties, inflicting his opinions on them whether they like it or not. Despite his naturally demure personality, Deku thinks that interfering in people's lives is a crucial element of being a hero.
His confidence and earnestness allow him to forge unbreakable friendships in the crucibles of trauma and trust, not to mention inspiring those who meet him to grow and evolve into better versions of themselves.
6 Deku Analyzes His Opponent Thoroughly
Those with brute force Quirks tend to rely a bit too heavily on their meta-abilities, often leading them to neglect the analytical facets of combat. On the other hand, Deku develops a sharp eye for fight choreography, noting his observations and evaluations down in a series of notebooks.
Deku's understanding of battle dynamics is on par with many Pro Heroes' and far superior to most students in his class, many of whom learn the basics of combat analysis from him.
5 He Tries To Save Bakugo Without Thinking
Deku's final glimmer of hope is extinguished when All Might tells him that a Quirkless person can never be a real hero. Regardless, he charges in guns blazing towards the Sludge Villain when he discovers that Bakugo's life is in imminent danger.
Deku's act is so pure and selfless that All Might instantly decides to select him as his successor, claiming that a true hero is someone who helps people on both subconscious and conscious levels.
4 Deku Protects Multiple Heroes From Shigaraki
Tomura Shigaraki all but destroys the group of Pro Heroes that have assembled in Jaku City, pushing both Endeavor and Eraser Head to the limits of their abilities with a host of new Quirks.
Tomura tries to kill a dozen birds with one touch, but Deku grabs the fallen heroes using his Blackwhip and triggers Float, his third Quirk, carrying everyone to the safety of the sky. In a single move, he saves Shoto, Rock Lock, Endeavor, Bakugo, and a couple of others from Tomura's Decay.
3 He Is Willing To Give Away His Precious Quirk
Nearly all of Deku's insecurities stem from his Quirkless status, so receiving One For All feels like a new lease on life for him. However, when Class 1-A faces Nine and his allies in My Hero Academia: Heroes Rising, they are quickly overwhelmed by the villains.
Bakugo and Deku pool their Quirks together, but this ultra-powerful combo fails to defeat Nine. Deku realizes that giving One For All to Bakugo is the only chance they have for victory, but he doesn't even flinch when transferring his beloved Quirk, such is his devotion to heroism.
2 Deku Saves Tenya From Making A Huge Mistake
Deku can't shake off the nagging feeling that Tenya isn't as cheerful as he claims to be. He eventually discovers that his buddy has gone after Stain to punish the latter for attacking and debilitating Tensei. Deku follows Tenya's trail and finds him at the Hero Killer's mercy.
Deku lands a powerful blow on Stain's face, saving Tenya's life and buying enough time for Shoto to join the battle. As it happens, Deku's meddling ways are almost always appreciated in My Hero Academia.
1 He Returns To U.A. For A Much-Needed Bath
Deku shoulders all the weight of being a Pro Hero but often forgets to cut himself some slack. He burns bright, but he also burns out quickly. Deku leaves U.A. following the Tartarus prison break in the hopes that the villains would leave his friends alone and target him instead.
Class 1-A bluntly denies his wish and chases after him, but Deku attempts to fight off their advances and escape. However, his classmates wear down his defenses, claiming that even the best Pro Heroes would falter without good food, sound sleep, and companionship.