In the attack, Sonic, using the power of the seven Chaos Emeralds, transforms into a very powerful version of himself that is able to fly quickly and attack fighters by ramming into them.
The screen zooms in on Sonic, and he transforms, using the transformation animation from Sonic the Hedgehog 2. When Sonic transforms, he gains the ability to fly around the stage at an incredible speed. The transformation lasts for about 15 seconds (though this can be extended by ramming into opponents and other things that can take damage, causing him to freeze for a moment), and is completely invincible for its duration. He is also unaffected by Bumpers. Sonic can attack in this form by simply ramming into opponents; the faster it is going, the more damage is dealt. When the opponent is attacked, the move deals about 35%, but the first attack is roughly 25%, and never lower (the attacks are variable in function of this speed: 12%/19% in SSB4). It is similar in function to Pikachu's Final Smash, Volt Tackle, except that it cannot go through hard platforms like Volt Tackle can (however, when Sonic is too slow or has stopped moving, he will be unable to go through soft platforms), and has better knockback and control. Super Sonic cannot KO himself when he reaches the blast line, regardless of how far it is going, but if he turns back to normal while he is too far away to recover, he will be penalized with a self-destruct.
Sonic's Final Smash is arguably among the strongest in Brawl, as the player cannot take damage for its entire duration, and cannot be KO'd, unlike other transformations such as Wario-Man and Giga Bowser. Furthermore, an experienced player who has learned how to control Super Sonic's unwieldy movement can use his high damage output, knockback, and speed to guarantee multiple KOs. Even then, he can fly around a single target and rapidly rack up damage in a focused vicinity, making him hard to avoid.
Super Sonic's attack power was weakened drastically in SSB4, though it is still a potent Final Smash.
Upon activating the Final Smash, Sonic says "Now I'll show you!" in Brawl, and "Super Sonic style!" in SSB4 and Ultimate. In the Japanese version of each game, he says "決めてやる!" (I'm going to settle this!).
The Final Smash returns in Ultimate largely unchanged in principle, but with one major alteration: the player has no control over his horizontal movement for the duration. He instead flies back and forth across the screen automatically (with even greater speed compared to the previous games), while the player can only control his vertical position. Overall, the move lasts for a much shorter duration, and can often be avoided completely by crouching. Contact with Super Sonic inflicts 6% damage for each impact and weak vertical knockback, however towards the end of the move, the knockback of each hit is increased, and the ending hitbox deals 10% damage and fairly strong vertical knockback.
In the Final Smash, the Chaos Emeralds appear briefly before Sonic turns into Super Sonic, and once he transforms back into Sonic. In the latter instance, the Chaos Emeralds fly off the screen in 3D.
In the games, Sonic has to collect all seven Chaos Emeralds, often hidden in Special Stages, in order for him to turn into Super Sonic. Whilst in Super form, Sonic will gain invincibility and a drastic increase in speed, sometimes accompanied with flight in later games, being able to damage enemies by touch. Super Sonic, however, can still be affected through falling into bottomless pits, being crushed or drowning. The Super form is temporary, requiring at least 50 rings before one can transform, which are drained at the rate of one ring per second by default while it's in effect. Having the ring count above zero is required to maintain the transformation, with the user reverting back to their normal form as a consequence of being depleted of rings. Starting with Sonic & Knuckles, Super Sonic plays a vital role in many final boss fights, often requiring the seven Chaos Emeralds to be obtained before the fight can be accessed, and with many later games, starting with Sonic Adventure, having Super Sonic available in the game solely during this fight.
In Ultimate, the transformation gives the stage a back drop resembling a black void. Locations like this have been the location of several final bosses in the series, such as Solaris, Alf Layla wa-Lyla, the Dark Queen, the Time Eater, and the Phantom King.
Sonic's Final Smash. The Chaos Emeralds give energy to all living things, and Sonic's gathered all seven of them, then used their power to transform into Super Sonic. His abilities in this form far surpass his normal ones, and he is even able to fly. He uses a lot of energy in this form, so he can only remain in it for a short time.
The Chaos Emeralds are said to hold enough power to control the whole world. It's that power that turns Sonic into Super Sonic. He turns a glorious golden color and can fly at nearly the speed of light. In his Final Smash, this high-speed flight damages anyone who gets in its way and can even launch them!