Shadow the hedehog is an anti-hero and one of Sonic's main rivals.
50 years ago, aboard the space colony ARC, Dr. Gerald Robotnik, Eggman's grandfather, researched and invented "project Shadow," the ultimate lifeformm, which will help for the better of mankind. Gerald Robotnik needed the blood of Black Doom, the leader of the black arms army, for Shadow to have life. Black Doom lives on the Black comet which returns every 50 years. Once Shadow was built, the Guardian Units of the Nation (GUN) feared Shadow's power and potential, so they forced Robotnik to shut down the program, the ARC with everyone still on it. A close friend of Shadow's and Gerald Robotnik's granddaughter, Maria Robotnik was shot after trying to escape the ARC with Shadow. Using Maria's final breath, she put Shadow in an escape pod and launched on to earth, imprisoning Shadow into suspended animation and giving him amnesia.
Instead of his traditional amnesiac hero self, he was basically turning into a curse-heavy Hedgehog.
He was using curse words (even made-up ones) in his sentences, especially to his allies or his enemies.
Shadow: I have you now, Motherfucker!
GUN Robo Fly Dog: Okay, this is a kid's-
Shadow: Loading. Loading. Error 404. Fuck Not Found.
Fly Dog: Godammit...
Shadow: Error 404. Fuck Still Not Found. But you're getting your ass kicked soon enough, motherfucker.