Notes

Izuku is a very timid, helpful, and polite boy, frequently overreacting to abnormal situations with exaggerated expressions. Due to being bullied for lacking a Quirk, he is initially portrayed as insecure, more reserved, and non-expressive. These traits are especially present around Katsuki, who constantly harangued him for his aspirations to be a hero. However, after being accepted into U.A. High School, making new friends, and facing Katsuki during the Battle Trial Arc, Midoriya gradually turned into a more confident and brave person, eventually developing leadership skills.

Izuku Mumbling
Izuku's mumbling habit.

Additionally, Izuku is a quite diligent and strong-willed student. His dream drove him to write down notes about everything he knows in regards to Heroes' Quirks. Because of this practice, Izuku has developed a great analytical mind and can form complex battle plans in seconds, which factor in both his allies' and enemies’ Quirks. Izuku externalizes his observations through endless mumbling, a habit which annoys or scares his peers. Izuku often writes down his observations in a variety of notebooks he titles as Hero Analysis for the Future.

Izuku is a caring person and never hesitates to rescue someone in danger, even if he knows that he is not strong enough to do it. Often, he does this on a whim, taking a more careless approach than the usual overthinking he goes through. Izuku often helps people with personal and emotional problems, even if it does not concern him, claiming that a Hero should meddle in other people's lives, though it could nonetheless lead him to be unduly meddlesome, annoying a few people he tried to help, particularly Katsuki. Still, Izuku's heroic spirit is recognized by many, having earned the loyalty and gratitude of characters that were previously antagonistic to him such as Tenya Iida, Shoto, Hitoshi Shinso, Kota Izumi, Sir Nighteye and even the Hero Killer: Stain, acknowledged Izuku as a true hero. Izuku even expresses concern for Ochaco Uraraka when she jumped in to calm him down after he lost control of Blackwhip which badly injured her, and also protected her from Hitoshi's capture weapon.

Izuku whatever it takes to be a hero
Izuku displaying his strong desire to be a hero by sacrificing his body.

Of all Heroes, the Symbol of Peace has impacted Izuku's life the most, seeing as how Midoriya models himself after the former Number One Hero. Many of Izuku's decisions and actions result from his desire to become a Hero similar to All Might, and thus he has a great devotion for him, to the point of collecting several pieces of various Merchandise related to the Hero and emulating several of his traits. Having inherited his Quirk, one of Izuku's current priorities is to be able to live up to his idol's legacy, as he is always looking for ways to improve his usage of One For All, being aware of the immense pressure that comes with succeeding the greatest Hero of all time.

Izuku appears to have a more brash and abrasive side to him. This typically shows up when he finds himself in combat. This side of him makes him act more like Katsuki, being rather loud and unwavering, and also with a strong drive towards victory. He claims that this is because he sees Katsuki as the embodiment of what someone who strives for victory should be. He has also admitted that he doesn't like this side of him very much and tends to keep it in check.

Abilities
Deku counters Katsuki
Izuku possesses moderate combat skills and fundamental fighting knowledge from his years of hero studies.

Overall Abilities: Izuku’s greatest asset prior to receiving his Quirk was his vast knowledge of fundamental hero skills and tactics. Izuku studied pro heroes for years and is able to apply that knowledge during crisis situations in a practical manner. His immense bravery and desire to become a hero was also a key factor greatly in helping his ability to protect himself and others. Before gaining his Quirk from All Might, he took on the Sludge Villain and rescued Katsuki Bakugo because of his boldness and applications of heroic skills.

Having been trained by All Might for 10 months in order to get his body physically ready to inherit One For All, he gained a muscular physique that allows him to perform at parameters higher than that of an average student outside U.A.'s hero course. After inheriting One For All from All Might, he was granted the ability to harness a stockpile of powerful energy. He could move faster than the eye can see and take down an enormous villain bot in a single punch. However, the physical backlash prevented Izuku from being able to fight properly or compete with his peers on an even playing field. Even so, he still possessed impressive physical durability, and his drive allowed him to withstand the drawbacks of One For All. Izuku's heroic traits, combined with his usage of One For All earns him 7th place in the U.A. Entrance Exam, having scored the most rescue points out any other applicant.

Despite the intense drawbacks of One For All, Izuku's wits allow him to use One For All in ways that are still effective in battle. He also retains his ability to act instinctively based on his notes and possesses basic hand-to-hand combat knowledge. This is shown when he is able to fight against Katsuki for a short time during the Battle Trial thanks to his knowledge and novice combat experience, even though Katsuki is the superiorly talented student. Even more impressively, Izuku was capable of overwhelming Shoto in close-combat because the latter was only using his ice. Shoto was the most promising student in Class 1-A at the time, even when only using ice, but Izuku was able to force the hybrid Quirk student into using his flames. When Shoto and Izuku were about to have a final clash with their powers at their fullest, the collision would’ve either destroyed (most of) the U.A. Stadium, or killed them both, if not one of them. This was prevented thanks to the intervention of Cementoss and Midnight, signifying how powerful Shoto and Izuku are when fighting toe-to-toe.

St. Louis Smash
Izuku improves to the point where he can defeat a powerful villain, such as Gentle Criminal, on his own.

Following his brief training with Gran Torino, Izuku gains more control over One For All. After learning he needs to make the Quirk apart of him, Izuku improves his overall fighting skills greatly. This led to the creation of One For All: Full Cowl, with Izuku gaining greatly enhanced maneuverability, strength, and a reduction in the physical backlash using his Quirk creates.[3] This allows him to compete more closely with his classmates in the physical aspects of the Hero Course and even allows him to fight properly against villains like the Hero Killer:Stain powerful S-Rank villain who had singlehandedly bested various Pro Heroes. After battling Stain, Izuku is recognized as one of stronger students of Class 1-A, as noted by Pixie-Bob.[4] During his battle with Muscular, an A-Rank villain whose physical strength and Quirk allowed him to endure 100% of One For All's power, Izuku was also able to successfully defeat the villain by going beyond One For All at 100%. Izuku stated that the entire Bakugo Escort Squad (consisting of himself, Shoto, Katsuki, Fumikage Tokoyami, and Mezo Shoji) working together, have the potential to take on someone of All Might's caliber.

As his mastery over his Quirk improves, so do his practical skills. His bravery, resolve, and intelligence remain steadfast, pushing him to get stronger as well. As his skills and experience increase, so does his confidence, and this confidence inspires his classmates. Shota Aizawa recognizes this and has identified Izuku as one of his class's two vanguards along with Katsuki.[5] Izuku eventually develops his own unique fighting style in order to separate himself from All Might. This further propels Izuku's skills to elite status. By their second fight, Izuku is able to fare much better against Katsuki. Even though Katsuki still holds the advantage in physical traits and wins, Izuku is able to injure him to some extent, showcasing his drastic improvement.

By the time of the U.A. School Festival, Izuku plays a key part in defeating several capable villains like members of the Shie Hassaikai, Himiko Toga of the League of Villains, and most prominently, Overhaul, the leader of the Shie Hassaikai who garnered the attention of All For One. Initially, the Yakuza leader overpowered the Nighteye Squad (which consisted of Izuku, Sir Nighteye, and Eraser Head), but Izuku, with Eri’s help, was able to unlock One For All: Full Cowl - 100% and successfully defeat Overhaul (who had merged with Rikiya Katsukame). After the Shie Hassaikai Raid, Izuku was able to best Gentle Criminal in battle on his own, even after the villain is empowered by La Brava's Quirk. After the battle, Izuku admitted that out of all the battles he has fought, the one with Gentle was the most difficult. This is mostly due to Izuku not wanting to fight him, and was sympathizing with Gentle throughout their battle.

Enhanced Endurance: Izuku has shown on many occasions that he is able to handle and bear with a lot of pain, such times are mostly because of the repercussion of over-using his Quirk. However, he can still manage to move his body despite feeling excruciating pain, which was seen in his battles against Muscular and Katsuki.
Keen Intellect: Izuku has proven to be exceptionally intelligent on many occasions, displaying both keen observation and analysis as well as adept intuition and resourcefulness. It is usually his intelligence that has helped him more than his Quirk. Izuku is a quick learner, being able to formulate strategies that take advantage of the situation and uses his knowledge to creatively utilize the Quirks of other people to their full potential, such as distracting Katsuki in their first mock battle and working together with Tsuyu Asui and Minoru Mineta to escape the villains at the flood zone in the U.S.J. Izuku also has extensive knowledge on Pro Heroes, his classmates, and their Quirks, as he takes note of them in great detail in his Hero Analysis for the Future. Because of his great admiration of heroes, Izuku has documented the history of many Pros, shocking even the heroes themselves.[6][7] His great foresight in this manner has earned him the praise and shock of many. Izuku's intelligence has allowed him to figure out One For All's mechanisms, allowing him to utilize the Quirk more efficiently in a short span of time. Gran Torino even compliments Izuku's intelligence, saying that Izuku is the type of person who thinks before he acts. After enduring the effects of the Bloodcurdle Quirk, possessed by Stain, Izuku was able to correctly deduce the Hero Killer's Quirk has a time limit that’s dependent on a target's blood type. Izuku's intelligence is so vast that it allowed him to rank 4th place in the academic exams, which proves that all of his training doesn't hinder his studies.[8]

During Provisional Hero License Exam Arc, Izuku also deduces the strategies of the schools and correctly figured they would come after his class first after seeing the U.A. Sports Festival; his warning his classmates prevents the "Crushing of U.A." In Class 1-A's match against Mirio Togata, Izuku is able to predict the latter's movements and could have landed a blow on the latter, had it not been for Mirio's Permeation Quirk. Despite not landing a hit, Izuku's deduction impressed Mirio. When he battled against Overhaul, Izuku decided to use Eri's Rewind Quirk to his advantage and use One For All to 100%, knowing she can rewind the damage.[9] As his battle with the Yakuza leader reached it's climax, Izuku was able to effectively exploit the time lapse that takes place when Overhaul has to heal himself after taking damage, and defeat the villain soon after.

Quirk
One For All 20%
Izuku utilizing 20% of One For All.

One For All (ワン・フォー・オール Wan Fō Ōru?): Given to him from Toshinori Yagi, a.k.a, All Might, Izuku's Quirk gives him access to stockpiled power, granting him superhuman strength and greatly enhanced agility and mobility by spreading his power through his body. Upon activation of Full Cowling, Izuku generates a whitish-green electrical discharge around his entire body.[10][11][12]

Though he has yet to demonstrate superhuman speed, immense reflexes, and durability on the level of All Might, Izuku has shown to be able to properly control a small percentage of One For All's power, using it to enhance his strength, speed, and agility. If Izuku does not keep One For All below his current limit of 20%, his body can be immensely damaged by the force of his movements. Izuku has also displayed a type of mental connection to the previous users of One For All.[13]

Recently, Izuku's reflexes and speed have improved with the use of One For All, being able to hold his ground against various incoming attacks during the Provisional License exam. Izuku's control of One For All has improved as his current maximum is 20% of One For All's power while in Full Cowl, at the time of U.A's School Festival.[14]

The core of One For All, which was hidden within the stockpiled physical power of Izuku's predecessors, possessed the Quirk factors of the previous generations, and have merged with it, causing it to continuously grow inside of Izuku. Eventually, Izuku will be able to manifest a maximum of six other Quirks, besides One For All itself. The known Quirk that Izuku has manifested so far is:

Blackwhip (黒鞭クロムチ Kuro Muchi?): The Quirk that had belonged to a bald One For All predecessor. It creates whips of black energy which can be used to grab objects from long distances, and can also allow the user to pull themself towards said objects.
Super Moves
Detroit Smash (デトロイトスマッシュ Detoroito Sumasshu?): The same as All Might's move, except Izuku does it in the form of an uppercut.[15]
Delaware Smash (デラウエアスマッシュ Derauea Sumasshu?): Izuku flicks his finger to create a powerful wind pressure shock wave that has enough force to break large chunks of ice.[16] Due to using this attack at 100%, it fractures said finger, limiting the time he can use this move without gravely injuring himself up to ten times.[17]
One For All Full Cowl 3
One For All: Full Cowl.

One For All: Full Cowl (ワン・フォー・オール フルカウル Wan Fō Ōru Furu Kauru?): Through his training with Gran Torino, Izuku was able to unlock this stage of his power and get better control of his Quirk. This technique allows Izuku to activate 20% (previously 5% which was then improved to 8%) of One For All throughout his body, letting the power course and flow through him instead of concentrating it in one location. According to Izuku, this technique gives him greater maneuverability.[18] Activating this technique gives him enhanced strength, speed, mobility, and agility. It also prevents him from breaking his bones when attacking. The cost of using this technique reduces the damage of how much his attacks do since instead of centering the power into a certain area, Izuku spreads it throughout his body.[11][19]
5% Detroit Smash (5 パーセント デトロイトスマッシュ 5 Pāsento Detoroito Sumasshu?): Izuku activates One For All: Full Cowl at 5% then jumps into the air and delivers an enhanced downward punch to the opponent.[20] He has also used this move in the form of a straight, forward facing punch.[21]
Double Detroit Smash (ダブルデトロイトスマッシュ Daburu Detoroito Sumasshu?): Izuku and All Might combine their Detroit Smashes into a single, devastating charge. They performed this final attack against Wolfram, shattering through a humongous chunk of metal and causing a huge explosion that destroyed Izuku's Full Gauntlet.
Delaware Smash Air Force (デラウエアスマッシュエアフォース Deraruea Sumasshu Eafosu?): Izuku uses his upgraded gloves that Mei Hatsume made for him to direct a blast of compressed air against his foe, possessing enough concussive force to stun Gentle while he was in mid-air, giving Izuku an opening to catch up to him.[22] By using all five of his fingers, he can launch up to four Delaware Smashes simultaneously.[23]
One For All - 30%: A technique that allows Izuku to use 30% of One For All throughout his body, giving him a higher boost in power and speed. This percentage was used in conjunction with Melissa Shield's Full Gauntlet, which nullified any drawbacks to using One For All at higher percentages. Because of this, it is unknown how this state affects Izuku's body under normal conditions. When using One For All - 30%, Izuku is able to effortlessly keep up with All Might's power, which was at 100% while the latter was pushing past his time limit.[24]
Izuku uses 100% on Muscular
A One For All Smash at 100%.

One For All - 100%: A technique that allows Izuku to attack using the full power of One For All in the desired part of his body, with the cost of said body part breaking upon execution. Further usage of the same limb after an initial attack can cause scarring, as seen with his fights against Shoto (causing Izuku to get surgery on his right hand due to injuries) and Muscular (leaving multiple scars across his right arm).[25]
100% Detroit Smash (100% デトロイトスマッシュ Hyaku Pāsento Detoroito Sumasshu?): This move involves Izuku activating One For All at 100% in his arm and then striking his target with a lunging punch.[26]
1,000,000% Delaware Detroit Smash (1000000% デトロイトデラウエアスマッシュ Hyaku-man Pāsento Derauea Detoroito Sumasshu?): This move is the strongest smash move in Izuku's arsenal, which involves him activating One For All at 100% during an adrenaline rush and then striking his opponent with a full-swing attack. When performing the move Izuku first uses a full-handed Delaware Smash, then delivers a devastating Detroit Smash. During the climax of his battle with Muscular, Izuku managed to overpower and launch his augmented opponent with enough force to create an impact crater in solid rock with the strike alone, thus defeating the villain.[26]
Full Cowl - Shoot Style
Shoot Style.

One For All: Full Cowl - Shoot Style (ワンフォーオール フルカウル シュートスタイル Wan Fō Ōru Furu Kauru Shūto Sutairu?): While using One For All: Full Cowl, Izuku uses a fighting style that focuses more on kicking.[27] Izuku concentrates One for All: Full Cowl's effects in his torso and legs rather than his arms, allowing him to put out even more power due to the fact that the human leg muscles are naturally stronger than the human arm muscles, granting him enough power and stability and allowing him to step away from the shackles of having to imitate All Might.
Shoot Style: St. Louis Smash (シュートスタイルセントルイススマッシュ Shūto Sutairu Sento Ruisu Sumasshu?) While using the Shoot Style, Izuku leaps into the air and before swinging around to deliver a roundhouse kick to the opponent's face. Izuku used this move to incapacitate Gentle Criminal, who had been empowered by La Brava's Lover Mode Quirk to match Izuku's use of One for All: Full Cowl at 8% of its power.[23]
One For All: Full Cowl - 20%: Izuku uses 20% of One For All's full power and distributes it throughout his body, giving him an even greater power and speed boost. While it won't cause his bones to break, it does put immense strain on Izuku's body, causing him great pain to the point that it feels like his bones are on the verge of breaking.[28]
Manchester Smash (マンチェスタースマッシュ Manchesutā Sumasshu?): Izuku leaps into the air and flips forward to bring down an axe kick upon his opponent. Although Kai Chisaki managed to evade it, the attack itself pulverized the ground thoroughly enough that Kai wasn’t able to completely retaliate with his Overhaul Quirk.[29]
One For All Full Cowl - 100%
Izuku uses One For All: Full Cowl - 100%.

One For All: Full Cowl - 100% (ワン・フォー・オール フルカウル 100%パーセント Wan Fō Ōru Furu Kauru Hyaku Pāsento?): Izuku activates One For All to its fullest extent throughout in Full Cowl, granting him a tremendous boost in speed and strength that allowed him to easily overwhelm the likes of Kai Chisaki. This was first used against Chisaki to protect Eri. The power increase seemingly gives him fire-like trails coming from his eyes and light colored hair. He can currently only use it infinitely with no damage done to his body while in physical contact with Eri. Since Eri has the ability to rewind the state of a person's body, any damage done to Izuku's body by using One For All at 100% would continually be undone by Eri's Quirk which proved useful in his fight with the villain.[30]