Air Wall

Air Wall was the unnamed Quirk used by Nine, who stole it from an unknown hero.

Description
Air Wall lets the user create circular shields made of compressed air to shield themselves. To create this defense, Nine needs to raise his hand in a particular direction at a time. These barriers can withstand powerful attacks such as Izuku's Delaware Smash Air Force. The barriers can also be layered for greater protection.

Nine can also use the shield to blast people away or fire powerful bursts of pressurized air able to knock down and even stun the opponent.

Weaknesses
Although extremely tough, the Air Walls are not indestructible. They seem to have more durability the more Nine is focused on them or is in good health. This is shown when Nine was physically weak due to his condition and the Air Walls just shattered upon impact compared to when he's at full strength and they are durable.

Air Walls are only created in the direction Nine raises his hand, so agile enemies can maneuver to avoid the shield and attack unprotected areas.