Anti-Sonic grew up in the shadow of his father, who helped move Anti-Mobius into a period of Great Peace but in the process neglected his son - embittering the young hedgehog and a mere ten years after the Great Peace begun Anti-Mobius found itself stale and degenerated: Anti-Sonic took the chance and overthrew his own father before teaming up wih Anti-Sally to usurp King Maximilillian and transformed Anti-Mobius into a dictatorship in which he and his Anti-Freedom Fighters ruled with an iron fist, their only resistance being Julian Kintobor (a benevolent version of Dr. Eggman).
Anti-Sonic first encountered Sonic when the heroic hedgehog took a detour through the Cosmic Interstate and became lost, winding up in Anti-Mobius, the two briefly fought one another until (somewhat ironically) Sonic was aided by Kintobor in defeating his evil counterpart: after this Sonic continued his trip along the Cosmic Interstate to return back to his native reality.
Anti-Sonic would returned however when the villainous Robo-Robotnik summoned him with the task of stopping all of his counterparts from guarding a giant hand which would activate the Giant Borg, a mission he gladly accept and accomplished, as Robo-Robotnik teleported the hand to his base while Anti-Sonic distracted the other Sonics. After this Anti-Sonic travelled to mainstream Mobius alongside his Anti-Freedom Fighters and began to terrorise the citizens of the planet until Sonic and his crew fought against them and sent them back to Anti-Mobius.
Anti-Sonic would afterwards return acting as Dr. Robotnik's ally, fooling Anti-Knuckles into helping him steal the Chaos Emeralds from the mainstream Floating Island and although the plan seemed to work at first Anti-Knuckles good nature coupled with the intervention of the Freedom Fighters meant that mainstream Knuckles had little difficulty defeating Anti-Sonic. After Robotnik was killed off in mainstream Mobius Robo-Robotnik once again recruited Anti-Sonic to track down the fragments of the Giant Borg (the same weapon Anti-Sonic fought an army of alternate Sonic's over to defend) - defeated on his first attempt he grew more confident after a second try and successfully collected all but one of the Giant Borg components. However Anti-Sonic mistook the other Robotnik with Robo-Robotnik and thus became trapped in that reality until he was rescued by Sonia and Manik: however his freedom was short lived as he was once again caught by Zonic the Zone Cop and sent to the No Zone as punishment for his crimes across the multiverse.
Anti-Sonic did not stay imprisoned long however and made his way back to mainstream Mobius only to suffer a fairly humiliating defeat by Antoine, resulting in Zonic taking him back to the No Zone. Yet Anti-Sonic just refused to stay down (a bit like his heroic counterpart) and soon escaped the No Zone again and returned to Anti-Mobius.
Upon returning to Anti-Mobius Anti-Sonic was confronted by Patch (evil-version of Antoine) and he defeated him, Anti-Sonic then proceeded to switch Patch with mainstream Antoine in order to torment them both - however he soon found himself impressed with how Patch began to use the opportunity to impersonate Antoine and seize power and decided to do the same thing to Sonic. During his time impersonating Sonic he made advances on many of the girls on mainstream Mobius but made a mistake when he tried to make a move on Rouge the Bat - she was not as easily taken in by Anti-Sonic's moves and in an attempt to impress her Anti-Sonic agreed to steal the Master Emerald for her.
However Sonic proved himself way more resourceful than Anti-Sonic had imagined and returned to mainstream Mobius to battle Anti-Sonic once again - the two fought until Locke appeared and teleported Anti-Sonic away from the Master Emerald - despite failing to impress Rouge Anti-Sonic did manage to give her a smaller gemstone and thus gained a continued partnership with her (though not the romantic one he desired).
Birth of Scourge
Anti-Sonic and Rouge would soon try and steal the Master Emerald again but had to battle Locke again: this time however Anti-Sonic didn't aid Rouge and instead took the opportunity to steal the Emerald for himself and attempted to go into a Super-Transformation as a "birthday gift" to himself - however Locke refused to let this happen and punched Anti-Sonic with a chaos-infused strike that left a scar on his chest - however Anti-Sonic soon recovered and had attained a partial transformation: his fur now green and his strength enhanced. Anti-Sonic then declared himself a "real scourge" and that the days of being a mere "evil-twin" of Sonic was over - he then brutally assaulted Locke and prepared to kill him but was stopped by Rouge, who told him that under her rules they would not kill.
Scourge decides to get revenge on Sonic instead and by using the power of Chaos Control he transported himself and Rouge to Knothole and attacked both Sonic and Shadow became weaker as the two hedgehogs ganged up on him and was overwhelmed when more of Sonic's allies came to his aid.
Taking Rouge with him he fled, pursued by a vengeful Shadow and the two seemed doomed until a Warp Ring portal appeared and saved them from Shadow's wrath: the Warp Ring had been sent by Doctor Finitevus who proceeded to explain to Scourge that he required assistance in his upcoming plans.