Shadow the Hedgehog

Shadow the Hedgehog is known as Sonic's rival in the Sonic the Hedgehog video games, first appearing in Sonic Adventure 2. He is the "Ultimate Life Form", having near-unlimited power such as manipulating space via "Chaos Control". Initially he and Sonic were enemies upon their first meeting, at the time Shadow was not fully recognized by the public so when Shadow stole a Chaos Emerald, said public believed Sonic to be the criminal. Only by saving the earth together (Super Sonic and Super Shadow) did everyone finally get used to Shadow's image and Shadow became a sort of friendly (if very intense) rival to Sonic.

Shadow's closest friends are Rouge the Bat and E-123 Omega. Rouge often lends Shadow a hand during his missions of infiltration, and Omega was often used for heavy firepower. Despite this, Shadow often worried about Omega's safety, like in Sonic Chronicles: The Dark Brotherhood, when he found that the Marauders kidnapped Omega and took him apart.

Shadow once had a close friend, Maria Robotnik, who was later killed by members of G.U.N. As a result, briefly Shadow held a grudge against humans, which was ironic considering Maria was human herself. It was until after the Black Arms' defeat in Shadow the Hedgehog did he decide to stop worrying about Maria and look into the present.

Unlike Sonic, who simply runs to achieve high speed, Shadow's shoes are fitted with a sort of air skates that allow him to glide on the ground once he started moving at a certain speed.

Trivia

 * In an official character poll regarding the Sonic characters, Shadow came second to Sonic in popularity.