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, 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. A powerful A-rank technique invented by the Fourth Hokage, Minato Namikaze, which he created by observing the Bijū Dama, Minato spent three years developing the Rasengan; his plan was to take the shape transformation of one's chakra to the "highest possible point" and then combine it with his chakra's nature affinity, creating a technique that did not need the aid of time-consuming hand seals to control. He died before he could accomplish this, but on shape transformation alone, the Rasengan is still a very useful, powerful, versatile, and difficult technique to learn and master.

The Rasengan does not require any hand seals to use, relying only on the chakra control of the user. In the case of Naruto, he uses a Shadow Clone to help with shaping the chakra into a sphere, similarly to how he does in SSF2. Once it is complete, it becomes self-sustaining, which does not give the Rasengan a definite limit. The compacted nature and moving speed of the chakra allows the Rasengan to grind into whatever it comes in contact with to inflict major damage. This tends to launch the target backward after being hit or, if the target is lying on the ground or being launched to the ground, the destructive force is enough to form a crater. The trapping effect the Rasengan has in SSF2 could be a reference to the Naruto: Clash of Ninja 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 invented the Rasenshuriken, a similar technique he often has the help of three Shadow Clones for, though by the time of The Last: Naruto the Movie, Naruto is able to create Rasenshuriken without aid.

Rasenshuriken requires a great deal of chakra to perform, as Naruto has been shown creating as many as three of them on his own before tiring out. 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 medical ninjutsu from healing said damage. Tsunade likens the injuries to poison, and warns that those affected by the Rasenshuriken multiple times may not be able to use jutsu 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.