Dark Sonic

Dark Sonic (ダーク・ソニック), also known as Dark Super Sonic, is Sonic's darker and angrier form. His first and only appearance was in the sixty-seventh episode of the TV show Sonic X when Cosmo is scared and Chris is injured by Black Narcissus of the Metarex. The multitude of fake Chaos Emeralds and Sonic's intense anger allowed him to achieve this transformation. While in this state, Sonic shows his fury by destroying the two prototype Metarex that Black Narcissus pits against him in just a few seconds in order to test his abilities.

Physical Appearance
Dark Sonic looks similar to Super Sonic, except he has a bluish-black color, a blue aura, and no pupils or irises when he is at his true power.

History
When Sonic first crashes into the Metarex's base in episode 67, his first comment, after mentioning how many fake emeralds there are, is "Ugh... suddenly I don't feel so great!" in the English version and "Ugh... just looking at them makes me feel sick!" in the Japanese version. These comments are prompted by the negative energy Sonic can feel from the fake emeralds. It is this dark Chaos Energy that incredibly intensifies Sonic's rage at seeing an unconscious Chris and a terrified Cosmo trapped, that causes him to turn into Dark Sonic. Sonic is completely consumed by this combination and he attacks, seeking complete vengeance. He quickly destroys both of the machines Black Narcissus designed to test Sonic's strength and speed. As Dark Sonic, Sonic seems to take a murderous pleasure in doing so, indicated by his mad cackling and evil grin beforehand. Sonic's powers fade when he is calmed down by Doctor Eggman, who declares he has never seen Sonic so worked up before. Eggman says he does not want to see Sonic act out of anger and rage and how it is not good for him. In the English version, Eggman also says that if Sonic lets his temper get the better of him like this again, he may become angry all the time, "like another certain hedgehog [they] know". This last sentence seems to refer to Shadow the Hedgehog.

Powers and Abilities
As Dark Sonic, Sonic demonstrates light-speed movements, high enough to tears through a robot multiple times in less an a second simply by dashing through it, while not even being visible.When in this form, Sonic can run up to 780 m/s, three times faster than the speed of light. He also possesses very high physical strength, enough to make dents in metal and caves in a robot's face with one punch. He also has the ability to teleport, allowing him to hurt or, in some cases, kill, his enemies in a matter of seconds.

Personality
Dark Sonic seems to relish the prospect of murdering the two prototype Metarex, as shown by his demonic grin and mad cackle. In this form, Sonic's rage is out of control and he has even gained the intention to kill. However, he can still control his actions to an extent, as this form is rooted in the darker aspects of Sonic's natural instincts, including the desire to live, trample, and impose over opposition, and on a metaphysical level, the natural occurrence and manifestation of loss, decline, destruction and death. Upon consuming a regular chaos emerald while in his dark form, his sanity will decrease rapidly with every emerald absorbed, and his ability to destroy his opponents becomes devastatingly more brutal.

Trivia

 * This transformation does not actually have an official name. It is most commonly called "Dark Sonic", but some fans also use the name "Dark Super Sonic" due to its similar appearance to Super Sonic.
 * When Sonic transforms into Dark Sonic, his voice sounds slightly lower, similar to Sonic the Werehog.
 * Dark Sonic and Darkspine Sonic are similar in that they are both transformations that are provoked by negative emotions, as well as having similar names and appearances.
 * When Dark Sonic shows his face for the first time, music that sounds like the Sonic X theme for Shadow the Hedgehog plays shortly before Dark Sonic takes off into battle.
 * The events leading to Sonic's transformation into Dark Sonic are paralleled in Sonic and the Secret Rings, resulting in Sonic becoming the extremely similar Darkspine Sonic, but differently colored.
 * After consuming all seven emeralds while in dark form, Dark Sonic will even have the intention to kill his friends.