When My Hero High School started, no one expected that One For All, a powerful quirk All That Can Be Transferred to Deku with a hair kick, would actually be a 7-in-1 deal. Starting in the Joint Training arc/Season 5, Deku began to display the Blackwhip, one of the items contained in One For All. From the middle of the Final War arc/Season 7, Deku is finally seen using Gearshift, which now allows him to use One For All as a whole.
All of the quirks within One For All are of a different nature and have different levels of effectiveness, and some of Deku's One For All Quirks are more useful than others. Deku, being the mastermind that he is, has used them all in various ways, from his encounter with Lady Nagant, to his confrontation with Shigaraki. Like any other action-packed series, events happen in a flash during battles, and need to keep track of everything, so here's a quick summary of all the issues contained within One For All that Deku can use:
1
One For All
Type: Emitter
One For All is the backbone of all the other quirks because, without One For All, all the quirks would be dead with their users. One For All has two main features: the first is its transmission, attribute that allows it to be passed from one user to another. Yoichi, All For One's brother, was the original user of One For All, until it was transferred to Kudo without Yoichi's knowledge. The “side effect” of One For All being transferred to another person is that the conscience of each user resides within the quirk. That's what Izuku sees in the world.
The second aspect of One For All is the accumulation of energy and physical strengthening. This wasn't apparent when Yoichi was its only user (and transmission, for that matter), but the more a quirk is passed on, the stronger it becomes. The downside, however, is that the One For All overrides its user's body if they already had the quirk before. Deku or All may have experienced this due to its strange nature, but it affected all other previous users, possibly killing its fourth user, Shinomori.
2
Gearshift
Type: Emitter
Gearshift belonged to Kudo, the second user of One For All. Because it's the last one Deku is allowed to use, not much is known about its functionality. Gearshift works as it sounds: just like when you change gears when driving a car, Gearshift controls the speed at which the object can move and, moreover, its trajectory as well. The original quirk Kudo could only control small things, so he used it on bullets, but now the quirk has already changed so that Deku can use it on himself. In that way, Gearshift works similarly to Uravity's Zero Gravity.
Deku used Gearshift to increase the speed of his already existing attacks, as seen in the Detroit Smashes heroic combo featured in the episode “A Chain of Events, Across the Ages”, and the manga's 369th chapter of the same name. Deku also used Gearshift combined with Fa Jin to make himself so freakishly fast that he defied physics, like a true hero. This condition, however, has the disadvantage of a large physical setback, Kudo even warned Deku not to overuse it because it could end up killing him.
3
Father Jin
Type: Emitter
The easiest way to describe Fa Jin is to compare it to a toy clock. Fa Jin conserves energy by making repeated movements, and this can be clearly appreciated when Deku conserves energy in his legs while jumping up and down when trying to escape from Lady Nagant. Deku often combines Fa Jin with other quirks. He first gained speed when he tried to reach the Sky Box after being dragged to Okuto Island by Toga. By activating Float and gaining momentum with Fa Jin and One For All, he was able to fly at an incredible speed.
Unlike Gearshift, it's unclear if the quirk has improved in any way since it was passed down from its original user Bruce, but what is certain is that it also works on One For All itself, promoting physical development.
4
The Concept of Risk
Type: Emitter
Perhaps the most curious of all the issues within One For All, Danger Sense is clearly a nod to Spiderman's Spider-sense, as it has a similar function. Danger Sense notifies its user of nearby threatsbut with a catch: as seen in Deku and Toga's encounter on Okuto Island, the fact that Toga himself was convinced that his actions were out of love and meant that there was no threat to Deku, Danger Sense did not work. It didn't matter that the quirk user saw him as a threat.
Danger Sense also does not guarantee that the user will be able to avoid an attack or mitigate the danger. It worked and alerted the Deku of Lady Nagant's bullets, but he took damage from them. In a way, it is a very annoying situation, as it makes the user aware of the danger, but finding out how to avoid it, if possible, is up to them.
5
Black whip
Type: Emitter
Blackwhip is the first additional quirk that unlocks Deku, it happened accidentally in the Joint Training arc. As described by its original user, Daigoro Banjo, it gives the user the ability to extend and use dark energy strings, pretty much like a whip. It's a very versatile quirk. It can be used for fast transportation, arresting enemies, rescuing peopleand as temporary supports for an injured limb.
Cellophane helped Deku control the Blackwhip, so now he can control not only how many whips he unleashes, but also their length and strength. An important thing that Banjo mentioned and not seen in other OFA materials is this the rule of the emotions, of the heart. If Deku is out of control, Blackwhip is out of control, too.
6
A smoke screen
Type: Emitter
The smoke screen is a definite quirk: with it, Deku is capable he emits thick purple smoke from his body allowing him to hide his location and distract enemies to get less time. Deku used Smokescreen in his encounter with Muscular, Lady Nagant, and Shigaraki Tomura. In the latter, he combined Smokescreen with Gearshift to make the smoke dissipate a bit and hide his Blackwhip attack.
While Smokescreen doesn't quite reach the heights of some of the Quirks contained in One For All, we do have some great help. With it, Deku can quickly escape, hide his location, and confuse his enemies. Deku is a smart character, which means that in his hands, Smokescreen has a lot of power to help the little hero out a bit.
7
Float
Type: Emitter
A quirk originally owned by Nana Shimura, Tomura Shigaraki's grandmother. Like Smokescreen, its main function is really simple: to make the user float in the air. Its combination with One For All's power and Deku's wit and AirForce moves allows him to fly at high speeds. Originally, Deku learned to control his body during midair training with Uraraka, and by the time of the Paranormal Liberation War arc, he had already mastered it. Float is also an effective way to avoid Shigaraki rot.
Some of One For All's quirks are more complicated than others, but all have been of great help to Deku in his quest to become the greatest hero of all time. It is important to note that, in the end, the hero does the quirk, not the other way around. Deku became big in My Hero High Schoolnot because he used these seven elements, but because of the way he used them, because of his wisdom and intelligence.