Rasengan

Rasengan, also called Power Strike, is 's standard special move in Super Smash Flash 2.

Overview
When performed, Naruto summons a Shadow Clone, and builds up a ball of spinning chakra in his hand. When the special move button is pressed again, Naruto thrusts the chakra ball forward. If the ball hits an opponent, it slowly moves forward, trapping opponents inside and dealing multiple hits, finishing the sequence with a stronger hit that launches opponents. The move can be charged to deal more damage, and the energy balls have two stages before their fully charged version, with the lesser charged version being weaker and smaller than the other. If the player tries to move left or right while Naruto is charging Rasengan, he will store the charge and dodge, giving him time to evade enemy attacks and continue charging Rasengan. Aside from being fully charged, the attack deals anywhere from 10% to 14% damage to the opponent if all the hits connect, with moderate knockback at the end.

Fūton: Rasenshuriken
Fūton: Rasenshuriken, also known as Wind Release: Rasensuriken or simply Rasenshuriken, is Naruto's fully charged version of Rasengan in Super Smash Flash 2. Instead of hurling the chakra forward as a ball, Naruto instead throws the chakra, now in the shape of a fūma shuriken. The projectile has decent range and flies horizontally, exploding after its travel. Much like with the standard Rasengan, opponents hit by the move are trapped for the move's duration and dealt up to 23% damage, assuming all hits connect. Additionally, if an opponent is close enough to Naruto when he activates the move, they will be paralyzed for a moment and take an additional 3% damage, as well as the full force of the projectile when it gets thrown.

Origin
The Rasengan is Naruto's signature technique in the  manga and anime. It is a powerful technique invented by  after observing the Bijū Dama. Minato spent three years developing the Rasengan, and planned to take his shape transformation to the "highest possible point", and then combine it with his chakra's s, thus creating a technique that does not require time-consuming s in order to be controlled. He died before he could accomplish any of this, however.

The Rasengan relies on the chakra control of the user. In Naruto's case, he uses a Shadow Clone to help with shaping the chakra into a sphere, similarly to how he does in SSF2. The compacted nature and moving speed of the chakra allows the Rasengan to grind into anything it comes in contact with, to inflict major damage. This tends to launch the target backwards after hitting them, or form a crater when touching the ground.

The trapping effect the Rasengan has in SSF2 could be a reference to the  series, where the Rasengan would trap and damage the opponent multiple times in succession.

Fūton: Rasenshuriken
After Naruto figured out the Rasengan's principles, Naruto ended up accomplishing Minato Namikaze's plan by inventing the Fūton: Rasenshuriken, a combination of his nature transformation and the shape transformation of the Rasengan.

The Rasenshuriken requires a great deal of chakra to perform. If he attempts to attack with the Rasenshuriken similarly to how he attacks with Rasengan, his arm ends up suffering severe damage.

After travelling a certain distance or colliding with a target that it cannot slice through, the central sphere of the Rasenshuriken detonates, producing a vortex of wind in the immediate area. Within this vortex, countless microscopic wind blades are created, which damage anything within the vortex at a cellular level and prevent any from healing said damage. , the leader of Naruto's home village, likens the injuries to poison, and warns that those affected by the Rasenshuriken multiple times may not be able to use ever again.

Trivia

 * If uses this attack after copying it from Naruto, a clone of Kirby will appear. However, this clone will not be wearing Naruto's hat.
 * Prior to v0.7 of the demo, the exploded ball of chakra would not move forward at all, instead remaining directly in front of Naruto.
 * Prior to v0.8a, fully charging Rasengan would instead allow Naruto to use Ōdama Rasengan, in which the ball of energy he hurls forward would expand to a much larger one, which had a massive, lasting hitbox that could deal strong damage and knockback.
 * Although the move has since been removed, the Ōdama Rasengan technique is used at the end of Naruto's Final Smash, Tailed Beast Rush.
 * Prior to Beta 1.2, a more powerful version of Ōdama Rasengan was used as Kyūbi Naruto's fully charged Akai Rasengan, named Kyūbi Rasengan. It was removed alongside Kyūbi Naruto.
 * Prior to v0.9a, Naruto would summon two Shadow Clones to help him charge the Rasenshuriken as it is released.
 * Prior to v0.9b, 's, 's Proto Shield, and 's PSI Magnet could not weaken, deflect or absorb the Rasenshuriken. However, Mega Man's Proto Shield could absorb some of the knockback, thus allowing him to recover more easily. This was fixed afterwards.