Shulk announces "Air Slash!" and propels himself into the air with a quick vertical slash in a spiraling motion. This first hit deals set knockback. By pressing the special attack button again at the end of the move, he can follow up with a second slash (an outward right-handed clearing slash) which knocks opponents away and gives Shulk a small additional amount of height. The move works similarly to Marth and Lucina's Dolphin Slash, except that it carries all the knockback on the final hit instead of at the beginning, and with the ability to hit twice. It is also slower and possesses a wider range along with variable damage and KO potential depending on Shulk's currently active Monado Art.
The attack does 11-12% damage with mediocre knockback without any arts, while doing 16% in Buster and having good KO potential in Smash mode. Being in the Jump Art increases the total vertical height of the move, allowing Shulk to recover from almost anywhere offstage so long as he still has his second jump. However, the extra distance (while being in Jump) and the increased knockback (with Smash active) can cause the first hit to knock enemies too far to connect with the second, especially if Shulk has rage.
Like most special attacks, the move can be reversed for a Reverse Air Slash. While this does not affect the move's knockback or damage, it can be used as a reliable KO option after a ledge trump due to the move's wide hitbox and quick startup compared to Shulk's other attacks.
As a recovery, Air Slash has the same perks and flaws as Dolphin Slash, giving good vertical height in exchange for negligible horizontal distance. While a decent recovery, it is also one of Shulk's optimal finishers for combo strings, as several repeated forward aerials while in the Jump Art allows him to drag opponents to the side blast line. This leaves him vulnerable, however, and is essentially a sacrificial KO if there are no platforms below him.
Performing the second slash gives Shulk slightly more vertical distance, aiding his recovery if he performs the entire move instead of just the first slash. In addition, starting the second slash at the last second before Shulk falls helpless gives slightly more horizontal distance than performing both slashes quickly, which can be useful if Shulk is unable to reach a ledge.
It should be noted that the first slash can only snap onto ledges if the player performs the second slash immediately when Shulk reaches a ledge; if not, Shulk will overshoot and become vulnerable to attacks. Additionally, the move has a larger edge sweetspot if Shulk faces towards it, making it risky to attempt grabbing a ledge in the opposite direction.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
Air Slash is one of Shulk's physical arts in Xenoblade Chronicles, learned at level 14. The art sees Shulk briefly jump into the air and unleash a sword strike. The move having two hits may be a subtle reference to the effect of Air Slash in said game, as it has the ability to inflict two status effects on the enemy: Break (making opponents vulnerable to Topple, which causes them to fall onto the ground momentarily) and Slow (which decreases movement and auto-attack speed) if the attack hits the enemy's side (as opposed to the front or back). The pink color of the Monado's beam is a reference to how pink is used to identify Break arts in the menus. Interestingly, the original move only hits once, with the second hit being added exclusively for the Super Smash Bros. series, while the first hit's animation is actually more similar to the slash Shulk does when using Monado Purge, as he spins around entirely during the move.