Sonic the Hedgehog (Dark Mobius) (Pre-SGW)

Early life
Sonic's early history was most likely largely the same as his Mobius Prime counterpart's. The point at which things differed was when Knuckles became corrupted by his chaos powers and decided to conquer Mobius.

Knuckles' descent
According to Knuckles, Sonic was jealous of him for taking out Dr. Eggman easily when Sonic had been trying to for years, as well as Sonic just wishing that he was as powerful as Knuckles.

While the Dark Freedom Fighters were developing plans to defeat Knuckles, with Sally looking for the Sword of Acorns and making alliances, Sonic had another plan, which he discussed in a letter to her to let her know what was going on. Although he did not trust Mammoth Mogul, he believed that his old enemy also wanted to stop Knuckles, and so they formed an alliance. Amy and Tails already had leads on a couple of the Chaos Emeralds, and, with Mogul's help, they planned to get all seven together in a couple of weeks. They succeeded in obtaining the seven gems, and Sonic was able to become Super Sonic. In the end, Knuckles, now known as Enerjak, took the Chaos Emeralds so that his power would remain unrivaled, and he soundly crushed his opponents, including Super Sonic.

Legacy
After his defeat, Sonic's Core was taken by Enerjak and his body became one of the many husks hanging in Enerjak's Citadel.