Super Knuckles

Super Knuckles (スーパーナックルズ) is the Super State of Knuckles the Echidna that is gained once all seven Chaos Emeralds are collected. The only appearances of Super Knuckles were in Sonic & Knuckles, Sonic the Hedgehog 3 & Knuckles, Knuckles the Echidna in Sonic the Hedgehog 2 and later in 2013 re-release of original Sonic the Hedgehog. This is the one of the only two transformations demonstrated by Knuckles in the Sonic game series, the other being Hyper Knuckles.

Appearance
Super Knuckles has a bright pink pulse to his body and a pink aura around him, but retains his basic physical form, unlike most other super transformations.

Powers and abilities
While in his Super State, Knuckles is granted the traditional invincibility towards any attack. All his physical attributes has as well be enhanced in this form: His strength has been increased greatly, allowing him to plow through any obstacles and his movements has been enhanced as well, vastly increasing his speed, jumping, gliding, climbing, etc. Like every other super transformation caused by the Chaos Emeralds, once he runs out of rings he loses his Super State.

Sonic the Hedgehog 3 & Knuckles
Knuckles is able to turn into Super Knuckles at the first time in Sonic & Knuckles as the player has collected all seven Chaos Emeralds from Special Stages. By then collecting 50 rings and pressing jump button twice, the player has activated the Super transformation for Knuckles. The player will lose one ring per second and when the ring count is on zero, Knuckles turns back to his regular form.

In the locked-on version of Sonic the Hedgehog 3 & Knuckles, the player is able to transform into Super Knuckles as well with the similar pattern from Sonic & Knuckles. However the player has to complete this time seven different Special Stages from Sonic the Hedgehog 3. If the player enters the neon flashing giant ring at Mushroom Hill Zone the player will lose Chaos Emeralds, which evoke Super Emeralds in Hidden Palace Zone, thus not being to transform to Super Knuckles anymore. By collecting Super Emeralds, the player is able to transform then into Hyper Knuckles.

Knuckles the Echidna in Sonic the Hedgehog 2
By locking-on Sonic the Hedgehog 2 and Sonic & Knuckles, the player is able to get normally Super Knuckles in Knuckles the Echidna in Sonic the Hedgehog 2 by collecting the seven Chaos Emeralds from Special Stages of the game. Super Knuckles' abilities in this game are identical to that in Sonic & Knuckles.

Sonic Chronicles: The Dark Brotherhood
Super Knuckles was also referenced in Sonic Chronicles: The Dark Brotherhood in the Chaos Emeralds part of the journal, stating that "Sonic, Shadow, Knuckles and a variety of people have been known to use the power of the seven Emeralds to transform into Super versions of themselves".

Sonic the Hedgehog (16-bit)
In the 2013 re-release of the original Sonic the Hedgehog, Knuckles is not only an unlockable game mode, but all seven Chaos Emeralds (and a new final Special Stage) can be enabled as a bonus with the enhanced level select code. By doing this, Knuckles can indeed transform into Super Knuckles with only the Chaos Emeralds, and is almost identical to his original appearance from Sonic the Hedgehog 3 & Knuckles. Despite this, Super Knuckles is considered completely non-canon in this game.

Archie Comics
In the Archie Comics, to set up a battle with Super Sonic, Knuckles' super form was dubbed "Hyper Knuckles", to avoid the monotony of two supers against each other.

Knuckles' first known transformation into his super form was when he went head-to-head with Super Sonic in a battle for the Chaos Emeralds, their battle eventually destroying the Zone they resided in. Knuckles later turned into Hyper Knuckles again to battle Master Mogul, along with Super Sonic and Turbo Tails.

Knuckles later obtained his super form to fight Hunter on Angel Island using the power of the Master Emerald. In this form, Knuckles looks almost demonic and appears to be in pain when undergoing the transformation. As Super Knuckles, Knuckles was able to stop a spear which sends its victims to the Egg Grapes and proceeded to attack Hunter, picking him up, spinning him around, and throwing him into the ocean where he drowned.

Trivia

 * Super Knuckles, unlike most other Super States, does not have a golden glow, but rather a pink one.
 * This transformation is similar or even the same as Hyper Knuckles.