Akai Rasengan

Akai Rasengan, also known as Vermilion Rasengan , was Kyūbi Naruto's neutral special move in Super Smash Flash 2.

Overview
When performed, Kyūbi Naruto enters his three-tailed form, creates a Shadow Clone, charges, with that clone, a ball of spinning red chakra, and then hurls it forward as an energy ball. Mechanically, the move works almost identically to 's Rasengan, as the ball of chakra explodes to a larger projectile if it hits an opponent. Like Rasengan, the exploded ball moves forward slowly, trapping opponents inside to deal multiple hits. Aside from being fully charged, the attack deals anywhere from 22% to 70% damage to the opponent if all the hits connect, with the strongest charge being capable of one-hit KOing opponents, and each charge deals strong knockback at the end.

Kyūbi Rasengan
Kyūbi Rasengan is the fully charged version of Akai Rasengan. Instead of a moving projectile, the ball of chakra explodes to a massive spiraling ball of energy. This technique can trap opponents inside its radius before blowing them away with incredible knockback, being capable of one-hit KOing opponents. Additionally, the move does not have to connect with an opponent for the chakra to explode. The attack hits opponents up to seven times and deals 10% damage with each hit for a total of 70% damage if all hits connect.

Origin
In the  franchise, Naruto, as a Jinchūriki, can use the Nine-Tails' chakra to assist in using the Rasengan to create the Akai Rasengan. Under this influence, Naruto can improve his use of the standard Rasengan and simultaneously make up for his shortcomings in performing the technique. The chakra shroud surrounding him serves as a shell to stabilize the Rasengan's chakra. Due to the influence exhibited by the Nine-Tails' chakra, this Rasengan changed from its yellow or blue color to a purple, orange, or red color, made stronger than its standard version. First used against Sasuke Uchiha in the "Valley of the End", this move was powerful enough to counter Sasuke's Habataku Chidori, and the two techniques clashed to create a hyper-dense chakra sphere that later exploded and destroyed half the valley in the process.

Trivia

 * Kyūbi Rasengan works almost identically to Ōdama Rasengan, which was Naruto's fully charged version of Rasengan prior to v0.8 of the SSF2 demo.