Hyper Sonic

From Sonic Retro

Hyper Sonic is a form similar to Super Sonic in that it makes Sonic faster, invincible, requires fifty rings and makes Sonic glow. It also saps away rings at the same rate of one per second.

However, in addition to requiring the seven Chaos Emeralds it requires the seven Super Emeralds from Sonic 3 & Knuckles which are obtained by entering a large ring with all seven Chaos Emeralds. Sonic is then warped to the Hidden Palace, where he is required to complete one of the Special Stages, which are the same Special Stages that you would get the regular Chaos Emeralds from in Sonic & Knuckles alone. Sonic glows the colors of the Chaos Emeralds in this state, can perform a "double jump" of sorts that can be aimed, and destroys any Badniks on screen. He also cannot drown.

This character was only available in Sonic 3 & Knuckles and has not been in any game since. In the Archie comics, Sonic has a form called "Ultra Sonic"; since this is a common misnomer for Hyper Sonic, and since it appears at the same time as Hyper Tails, it may have been based on Hyper Sonic.

Sonic the Hedgehog series characters
Heroes	Sonic (Super, Hyper, Darkspine, the Werehog) | Tails (Super, Turbo) | Knuckles (Super, Hyper) | Amy Rose | Cream | Blaze (Burning) | G.U.N. | Silver (Super)
Anti-heroes/Neutrals	Shadow (Super) | Rouge | Chaotix | Mighty | E-102 Gamma | Chaos | E-123 Omega | Emerl | Rogues
Villains	Dr. Eggman/Dr. Ivo Robotnik | Metal Sonic | E-Series | Biolizard | Black Arms (Black Doom) | Gemerl | Fang
Other	Gerald & Maria Robotnik | Big | Chao | Tikal | E-101 Beta | Flicky | All Characters