Confusion (ねんりき, Mindpower) is Mewtwo's side special move. Mewtwo psychokinetically whirls the opponent in front of it around and lets the opponent land clumsily on the ground, doing some damage in the process.
Confusion's primary function is as a special grab. Upon using the move, Mewtwo will perform a swiping motion; if an opponent is in front of it, the opponent will be grabbed, twirled around a bit, take 10% damage in Melee or ≈9.0495% damage in SSB4, and begin tumbling downwards facing away from Mewtwo in Melee and towards Mewtwo in SSB4. As a grab, the move is unblockable.
Confusion's secondary function is as a reflector. In Super Smash Bros. Melee, it is unique in a generally unproductive way: reflected projectiles remain the property of their original owner, so Mewtwo cannot actually damage opponents by reflecting their projectiles (unless the projectile can normally hurt its owner). This is changed in Super Smash Bros. 4, as reflected projectiles are now able to hit their original owners.
Confusion can execute both of its functions simultaneously if both a projectile and an opponent are in range of the move. For example, Mario's Fireball can be reflected back onto him at the same time as Confusion spins him around, causing noticeably more damage than usual. In Melee, this can cause the Soul breaker glitch if the projectile is too strong to be reflected, causing the spun opponent to be indefinitely attached to Mewtwo until it is KO'd.
Using Confusion will halt Mewtwo's sideways momentum if it is grounded, and like Mario's Cape, will give it a small vertical hop the first time it's used in the air.
Unlike other aerial grabs, Confusion holds the opponent at a distance from Mewtwo as it falls downwards. As characters being thrown are not checked for terrain collision, this opens up a gimmick where Mewtwo can use Confusion to pull opponents down through solid thin platforms, most notably the sides of Battlefield. If done correctly, the opponent will be caught underneath the stage, which can cause them to panic, waste their double jump and/or triple jump, and be unable to recover. If the platform is too thick, the opponent will be pushed outside the stage and likely grab onto the edge.
Overall, while the "edge trick" is something that opponents must be wary of, Confusion is widely considered a poor and ineffective move in Melee. While its grab range is surprisingly large, it is outclassed by Mewtwo's normal throws (for damage, combos, and KOs) and powershielding (for reflection); even if the move connects, every character in the game can subsequently punish Mewtwo with a back aerial during its ending lag. However, SSB4 has improved the move's utility greatly; it is no longer as punishable, and as a move which both reflects projectiles and stops opponents in their tracks, it is fairly effective for disrupting approaches or setting up attacks.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
Like the other DLC characters, Mewtwo lacks custom move variations (aside from the glitch ones in 1.0.6).
Confusion is a special Psychic-type attack from the Pokémon series that was introduced in Generation I. It is often learned by Psychic-type Pokémon at low levels, considering the move's weak power, and has a small chance of confusing the opponent (hence its name). In all games, Mewtwo is able to learn Confusion at level 1, though it requires a Move Reminder to actually learn it after being caught since the Pokémon is usually encountered at much higher levels.
In the anime, Confusion could be used to halt and throw a Pokémon or a projectile through telekinetic powers, resembling its effect in Smash.