Katsuki is a young man of average height, with ash blond, spiky hair and red eyes. At school, he wears the standard U.A. uniform save for the customary red tie. Underneath his blazer, he wears a white button-up shirt with the first couple buttons undone. Despite wearing a belt along with the uniform's green pants, Katsuki does not pull them up all the way, giving his pants a baggy appearance.
His Hero Costume is composed of a fitted black sleeveless V-neck tank top with an orange X with the top half borders his shirt collar. His costume also has a seemingly metallic neck brace fashioned and used as a collar with three holes in both sides. His sleeves reach from within his large grenade-like gauntlets to his biceps. His belt, which also carries grenades, holds up his baggy pants with knee guards. He occasionally wears his hero mask that has large, flare-shaped cloth.
Katsuki is a very crude, violent, arrogant, and aggressive person. Having an attitude reminiscent of a teenage delinquent, Katsuki tends to come off as very anti-heroic, if not downright villainous. This problematic behavior goes all the way back to his early childhood days, when he was known to bully a young, Quirkless Izuku Midoriya. However, after being accepted into U.A. High and experiencing several personal defeats, one of them even coming from Izuku, Katsuki has gradually changed into a less antagonistic person, albeit still retaining a lot of his unpleasant traits.
Brutal and bloodthirsty, Katsuki smiles eerily when finding himself in the middle of a battle. His personality reflects his fighting style: mercilessly assaulting the opponent and having no regard for nearby objects, merely destroying them with his power. Despite this, he's quite talented in fighting, using his Quirk in various ways besides attacking. He's also very intelligent, being capable of strategic planning and holding some of the highest grades in his class, to the point that some even consider him a natural genius.
While not the most mentally stable hero-in-training, nor having the image of one, Katsuki knows who his enemies and allies are. Cold to his allies, though not to the extent of friendly fire, but colder and brutal to his enemies. He's also very rude and foul-mouthed, which makes him unpopular with most of his U.A. classmates. As the series progresses, his outbursts become less aggressive, usually becoming more comical, as he mostly gets angry at even small things like teasing. With that in mind, Katsuki seems to mature slowly but is still quite aloof and solitary, showing disinterest in hanging out with his fellow classmates.
Katsuki's aggression is reflected in how he uses his Quirk. He tends to completely disregard the notion that Quirks shouldn't be used in public, and will activate his Quirk for a number of reasons, such as to intimidate someone, to punctuate a point, out of frustration, or even if he just feels like showing off. When in combat, he will often set off smaller explosions in his hands, and sometimes will detonate even larger ones, when he's not even attacking, which highlight his aggression, particularly in combat. He thinks little of the laws regarding Quirk usage, and even berated Izuku for not using his own Quirk against Shigaraki in public.
Due to the constant praise of his abilities and his powerful Quirk, Katsuki has a superiority complex and wants to be first and the best at everything. He doesn't like when people look down on him, as if they were superior; thus, it diminishes his already short fuse. Despite his extreme arrogance, he also thinks of people such as Izuku Midoriya as an obstacle on his path to becoming the greatest hero. Because of his complex, he's implied to be anti-social; he seems not to care for much people as he doesn't remember his classmates' Quirks or names despite being in U.A. for some time, suggesting he refuses to acknowledge individuals who he believes are beneath him. He does, however, remember the names of people who give him a challenge or whose ability he respects, such as Ochaco Uraraka and went as far as to defend her when his classmates referred to her as a fragile girl.
Katsuki is also immensely prideful, as he hates the idea of others either helping him or having to rely on others to assist him in battle. Because of his pride, Katsuki refuses to work together with others, claiming he can do whatever he's assigned on his own. His pride has cost him on numerous occasions: he lost the Battle Trial due to his lack of cooperation with Tenya and he was effortlessly defeated by All Might in the End of Term Test. His pride is so intense that when pitted together with Izuku against All Might, he outright refused his partner's help, saying that he'd rather lose, but when the situation became critical, Katsuki was able to (reluctantly) put his pride to the side temporarily so that he could cooperate with Izuku. Katsuki is not against repaying those who help him, such as when he gave Eijiro the money for his broken night vision goggles when he came to his rescue. Still, due to his childhood experiences, Katsuki has difficulty doing the same thing towards Izuku.
Ironically, his inspiration for becoming a hero was the same as Izuku's, the Symbol of Peace, All Might. However, their beliefs differ: Katsuki feels a hero should never stop fighting or give up, regardless of the threat they face, and that always winning is the mark of a true hero. Furthermore, because of his arrogant and conceited behavior, various heroes, civilians and even villains have commented on his villain-like behavior. However, Katsuki is unwavering in becoming a hero, having outright refused Tomura's acceptance into the League of Villains.
Quirk and Abilities
Explosion (爆破 Bakuha?): Katsuki's Quirk allows him to sweat nitroglycerin and detonate it at will to create explosions. The more Katsuki sweats, the stronger his explosions become. As stated by Best Jeanist, Katsuki has a strong grasp on the applications of his Quirk. Katsuki usually uses small, powerful explosions from his hands to not only blast his opponents, but to propel himself and navigate through the air as well. He can keep up his explosions long enough to negate Shoto's Giant Ice Wall and even break through Eijiro's hardening Quirk. The blasts are powerful enough to send Katsuki flying at his opponents without much time for them to react, and he can use them swiftly enough to evade incoming attacks, even in the air. His most powerful explosion so far (without the need of the Grenadier Bracers) was used to completely destroy Ochaco's meteor shower, and blow her away with the following shock wave that rocked the entire Sports Festival stadium. Non-enhanced explosions of similar strength were used against All Might during the practical exam. These explosions, especially when used repeatedly in rapid succession, were actually shown to have a negative impact on Katsuki's arms.
Katsuki suffers somewhat from the impact of his explosions due to recoil but the overall effect is minimal given his physical prowess. He is able to set off constant explosions around him without feeling any negative repercussions even after many powerful blasts. However, overuse can result in Katsuki hurting his arms from the recoil of powerful explosions. This is shown in the practical exam when All Might notices the damage Katsuki is inflicting on himself and decides to knock him out to prevent him from permanently damaging his arms.
Another drawback of Katsuki's Quirk is that he is unable to use his explosions in areas filled with flammable gas as his explosions would ignite the gas and spread it further. Additionally, because his Quirk relies on his hands sweating, it is more difficult for his Quirk to work in colder climates. Without sweat from his palms, he cannot use his Quirk to it's fullest potential.
- Blast Rush Turbo (爆速ターボ Bakusoku Tābo?): Katsuki throws his hands back and uses explosions to propel himself. He uses this both on the ground to increase his speed and through the air to achieve a pseudo form of flight. He first used this technique on the ground during the Quirk Apprehension Test. . The first time he used it to fly was during the Obstacle Race. 
- Stun Grenade (閃光弾 Sutan Gurenēdo?): Katsuki starts creates a sphere of light between his hands that explodes into a large scale flash. Similar to the effect of an actual stun grenade, the flash of light blinds anyone close by. He first used this technique to defeat Fumikage Tokoyami.
- Howitzer Impact (榴弾砲着弾 Hauzā Inpakuto?): Katsuki takes to the air and uses explosions to propel himself in a circular motion to create a tornado. This tornado builds up oxygen to fuel the incoming explosion. After colliding with the ground, Katsuki releases the powerful aforementioned explosion. Present Mic compared the effectiveness of the technique to that of an actual missile. Katsuki first used Howitzer Impact in the final match of the U.A. Sports Festival Finals. 
- AP Shot (徹甲弾 (A・P・ショット) AP Shotto?): Katsuki's special move. Katsuki stretches out one of his hands and uses his other hand to form a circle on the palm of his outstretched hand. Katsuki then fires an explosion through the circle, which creates a concentrated blast beam. By focusing his the path of his explosions into a single point instead of around his whole palm, Katsuki creates a concentrated blast with reduced area of impact, but with enough power to successfully pierce even solid concrete.
- AP Shot: Auto-Cannon: A rapid-fire version of his AP Shot technique. The explosion power is reduced in order to avoid dealing severe damage to human targets.
Overall Abilities: Katsuki has shown to be one of the strongest students on Class 1-A. He was able to defeat Fumikage Tokoyami and Shoto Todoroki during the Sports Festival, people who are also considered to be quite strong (although they had disadvantages respectively in their fights against Katsuki but despite these limitations they still proved to be strong). Many notable Pro Heroes such as Shota Aizawa and All Might have praised Katsuki's prowess; even the League of Villains have taken notice of Katsuki's strength and went as far as kidnapping him even if it meant losing members of the Vanguard Action Squad, as his potential membership would have far exceeded the risk.
Enhanced Strength: Katsuki possesses an above average physical strength, as he was able to fight on par with Izuku even when the latter is using his Quirk. He was also able to pressure and overpower Shoto Todoroki, a powerful combatant, during their battle. He is able to use his Grenade Bracers without any recoil due to his strength, whereas Izuku nearly dislocated his arm just from using one.
Keen Intellect: Katsuki has proven to be very smart and strategic, as he was able to figure out Kurogiri's Quirk weakness and Fumikage's weakness in a short period of time. Additionally, he quickly assessed which of the attacking villains in USJ was the most dangerous threat in the long term. Even Pro Heroes (such as All Might) have mentioned several times his great potential and battle-sense. Shota Aizawa stated that in battle Katsuki shines his brightest. Further proving his intellect is that Bakugo had the 3rd highest score in the midterms from 1-A, being even higher than Izuku's, who scored the 4th highest.
Grenadier Bracers (籠手 Kote?): An adjustment added to Katsuki's hero costume that stores his nitroglycerin-like sweat. Once filled he can pull the grenade pin in order to release a large blast, as shown when he fought Izuku in All Might's Heroes vs. Villains test. It has enough explosive power to destroy all parts of the building within its blast radius. This equipment was first used during the Battle Trial.
Improvised Grenades: Around the belt of his Hero costume, are several containers made to look like hand grenades. These can store Katsuki's nitroglycerin-like sweat, and be used as regular grenades at a later time. These were first used in a practical way during the Provisional license exam by Denki.
Knee Pads: These are very blunt metallic attachments to Katsuki's knees. They are designed so he can "kill with his knees", but he has not displayed such use for them as of yet.
- Originally, Katsuki was supposed to be a natural born genius, a very kind and gentle character who spoke without thinking and unintentionally insulted others. The author, however, found this original draft to be boring and decided to make him an unpleasant character instead.
- Katsuki's academic data at U.A. is as follows:
- Katsuki likes spicy food and mountain climbing.
- Katsuki's rankings in the Popularity Polls are as follows:
- Katsuki's name is composed of "爆" (baku?) from "爆破" (bakuha lit. "explosion"?) and "勝" (ka(tsu)?) from "勝つ" (katsu lit. "to win"?).
- With his birthday taking place in April 20, Katsuki is the oldest kid in Class 1-A, as everyone was 15 when they started U.A.'s school year in early April.
- (To Izuku Midoriya) "From here on, I..! From here on..! Y'hear me?! I'm gonna... beat you all! Enjoy your win. It'll never happen again! Dammit!"
- (To All Might) "Needless to say... I'll be a hero that surpasses even you!"
- (To Shoto Todoroki) "You'll regret making a fool of me! I'll freaking kill you! I'm taking the first to end all firsts! There's no point in winning against some half-assed punk! No point if I can't do better than Deku! So if you're not trying to win, get the hell outta my face! Why're you even here, you bastard?!"
- (To Izuku Midoriya) "Stop talking. I will win. That's... what heroes do."
- (To the League of Villains) "Can't stand morons like you who can't get to the damned point! Basically you're saying, 'we wanna cause trouble, be our pal!' What a joke! I've always admired All Might's triumphs. No matter what any of you jerks say... Nothing's ever gonna change that!"