As of now, Deku has access to seven Quirks, namely One For All, Transmission, Fa Jin, Danger Sense, Blackwhip, Smokescreen, and Float. The basic gist of all these powers is that they all come from the previous One For All users, with their abilities becoming stronger throughout the generations.
Deku's final quirk is known as 'gearshift'. It's a quirk that is activated via physical contact. It allows the user to change the velocity of anything they touch, meaning they can spontaneously slow things down, or speed things up.
Because of this, in truth, Deku has not one, but seven Quirks, stored in One for All's core and passed down from user to user. As the series goes on, the hero in training begins manifesting all these abilities one by one, being forced to adapt to and train each of them, in order to control them and use them in battle.
Deku's second Quirk is known as Transmission in My Hero Academia. In Chapter 349 of the My Hero Academia manga, the second One For All user revealed this about his power: "Mine has transformed into a very useful but specific type of power." Not much was known about it until Chapter 368 came out.
The seventh user of One For All, Nana Shimura is a superheroine with the Quirk, Float. She was a friend of Gran Torino and All Might's mentor, teaching him in an optimistic manner.
By the end of chapter 317 (Dark Hero Arc), Deku had the makings of a villain in both power and appearance. He became exhausted and angry with himself for his actions, only strengthening Black Whip's powers.
One For All is one of the strongest Quirks in My Hero Academia, if not the strongest. It allows the super to stockpile incredible amounts of power within their body which, when released, grants a tremendous boost in power.
As of now, Deku has access to seven Quirks, namely One For All, Transmission, Fa Jin, Danger Sense, Blackwhip, Smokescreen, and Float. The basic gist of all these powers is that they all come from the previous One For All users, with their abilities becoming stronger throughout the generations.
Izuku was raised primarily by his mother Inko, who has the ability to make small objects float towards herself. His father, Hisashi, whose quirk allows him to breathe fire, is not seen due to him working abroad in the United States.
1 Shigaraki
All For One is arguably the rarest and most powerful Quirk possessed by any villain in My Hero Academia. This Quirk so thoroughly defines its bearer that he's taken it as his name.
Fans know that his name is Hisashi Midoriya and that his quirk is fire breathing. It's assumed that Hishashi's fire-breathing quirk isn't as eye-catching as Dabi's flames since Inko brushed it off at Izuku's doctor's appointment as a child. Currently, Hisashi's work has taken him abroad, leaving Inko and Izuku alone.
Garaki specifically stole Deku's quirk from him as a child because of its impressive potential, it's also likely that same quirk could've been the ability that All For One chose to pass down to his quirkless successor, Shigaraki.
According to the events of My Hero Academia so far, Deku grew up without a Quirk. He was given the OFA Quirk when he met All Might. The series does give an explanation for why Deku was deemed Quirkless. With that said, more than a few fans are skeptical about it.
Bakugo was stronger than Midoriya, though he indicated that Midoriya could eventually surpass him.
Deku had unlocked all but two of the Quirks in One for All prior to episode 20 of season 6, leaving only the Second and Third User's Quirks unknown. However, these two did not seem to approve of Deku, and when he spoke to One for All's previous users in My Hero Academia, they faced away from him and said nothing.
One For All: All Might inherited the Quirk called "One For All." It would allow him to stockpile an enormous amount of raw power, allowing him to significantly enhance all of his physical abilities to a superhuman level.
Yoichi Shigaraki was the first user of One For All and quite possibly the weakest of the lot. He is known to have been sickly and his brother, All For One, often took pity on him. After his brother passed on an energy stockpiling Quirk to him, Yoichi eventually went on to create the One For All.
Whenever a hero engages in battle, there is the expectation that parts of their costume will get ripped up or destroyed. With his mask being the first piece to suffer this, as it was not well-designed, Deku likely realized there was no point in having it be constantly repaired or remade by the school's Support Course.
Izuku Midoriya has been betrayed by U.A and his classmates besides two. Kyoka Jiro and Katsuki Bakugo.
Sometime later he would be scouted by Shigaraki, the leader of an organization called the league of villains, and thus putting him on the path of villainy. The second route AU's usually take is that Deku actually follows Katsuki's advice, but is saved by the league of villains.
In order to try to protect people, Izuku left UA and is working with All Might and an elite squadron of heroes as he goes through his Batman phase—better known to fans as Dark Deku.