Smokescreen

Smokescreen was the emitter Quirk originally held by En Tayutai, handed down to Izuku Midoriya through One For All, and finally forced into Tomura Shigaraki by way of blood transference. Rated long range, it surfaced in Chapter 307, took its name in Chapter 308, and reached the anime in Episode 132.

The user's body produces a dense purple cloud that can be pushed out over a very wide area, blotting out an opponent's sight and opening the door to an ambush.

The drawbacks stack up. Release too much and the haze swallows the user's own vision, which invites a counterattack from whoever finds them first. There is no offensive application at all, and En judged that the Quirk could never be developed to the Ultimate Move level. Humidity chokes its spread, so rain limits how far it travels, while a strong enough shockwave scatters it outright, something Katsuki Bakugo demonstrated with Land Mine Blast.

En almost certainly paired it with One For All, though how skilled he was with it was never recorded. Izuku awakened the Quirk not long after the Paranormal Liberation War and tried it out against Muscular during the villain's rematch. One For All's stockpiling had made the smoke far stronger than in En's hands, and between that surge and his own inexperience, a startled Izuku dumped out so much that it wrapped around him and cost him his own sight. Once he recovered, he used Float to rise over the city and laid the smoke across the streets, cutting Muscular's visibility and steering him toward a chosen spot.

Against Lady Nagant he opened with the Full Blast Ultimate Move, which unloads a huge volume of smoke at the cost of possibly blinding himself, buying the seconds he needed to close in using Fa Jin. He folded the Quirk into the combined attack that drew on every power inside One For All when he faced Tomura Shigaraki, and later paired it with Gearshift's Low Gear so the cloud lingered while he called up Blackwhip, a combination the anime tinted blue rather than the usual purple. He even exhaled it as a breath weapon during that fight. Shortly afterward Izuku tried to push all his remaining Quirks into Tomura and destroy him from the inside; only En and Smokescreen completed the transfer, tearing away part of Tomura's soul and consuming the Quirk itself. Robber Villain's Smoke is a near relative, minus the eye irritation.