My Hero Academia explained the quirk belonging to All For One's mysterious assassin, Lady Nagant! Izuku Midoriya is now working mostly solo these days with support from All Might and the top three pro heroes, but it's due to the fact that all of them have been waiting for All For One and Tomura Shigaraki to make their movie. Izuku has been trying his hardest to strengthen his use of One For All before this happens, but the previous chapter of the series revealed that his time is already up as a new mercenary has set their sights on him.
The previous chapter of the series saw Izuku Midoriya in the crosshairs of a mysterious sniper sent by All For One, and the newest chapter of the series revealed just how dangerous this villain truly is by fleshing out her quirk. With her quirk, Rifle, she's essentially a perfect sniper rifle in human form. This is going to be quite the tough challenge for Izuku Midoriya, and this is only the first of All For One's mercenaries.
Chapter 312 of the series reveals that Izuku figured out immediately that this sharpshooter was a former hero turned villain named Lady Nagant. As demonstrated by the gun that forms out of her right arm, Nagant has an even more dangerous ability thanks to her hair. She can take pieces of her hair and form them together like epoxy putty. Then they harden and become any kind of ammo that she needs.
As the pro hero Snipe describes in a flashback (which is how Izuku knows about Nagant's ability), Nagant already had the eyesight capable to pull off impressive long range shots. We see this in action as she is able to hit Izuku with the bullets, and the strength of these hits is enough to send him flying (as he notes that they hit harder that Howitzer Shots). Izuku's able to deflect two of her shots, but this is really only the beginning of the fight.
It's soon revealed that Nagant also has the "Air Walk" Quirk thanks to All For One, and together with her Rifle ability, Izuku Midoriya's going to need to use all kinds of tricks in order to fight off Nagant's assault. Let us know your thoughts in the comments or you can even reach out to me directly about all things animated and other cool stuff @Valdezology on Twitter!