Shadow the Hedgehog (Light Mobius)

King Shadow the Hedgehog was the king of Mobius and the husband of Sally Acorn after the timeline of the Mobius: 25 Years Later was altered by King Sonic. King Shadow ruled over the planet with an iron fist, eliminating those he deemed enemies, and going so far as making Maria an object of worship. His brutal rule came to an end after Lara-Su used his knowledge of Chaos Control to place him in suspended animation for centuries to come.

Ruler of Mobius
When the timeline of the Mobius: 25 Years Later universe was changed, it altered events and made Shadow the ruler in Sonic's place, as the blue hero had disappeared from the scene. During his tenure as king, Shadow made Knuckles his "legitimate" chief enforcer, while making Lien-Da his informal chief enforcer as well as leader of the Dark Eyes. After King Sonic had returned from his excursions to the past, he was located by Tails and joined forces with him and Lara-Su to take down King Shadow. Due to his Chaos-derived reality warping abilities, Shadow was fully aware that history had been altered, and so was determined to keep anyone from acting on it. Thus, Shadow had enforcer Knuckles arrest the three for "treason". (StH: #166)

Defeat
Sonic and the others then escaped from Castle Acorn's dungeon thanks to Knuckles, who had only been working under Shadow to help defeat him. Shortly afterwards, Shadow found himself facing up against the aged and former King Sonic, though managed to defeat him with almost no effort, as Sonic had physically aged and grown weak while Shadow had not. Lara-Su soon joined the battle however, and after a brief fight, she used her own knowledge of Chaos Control to place King Shadow in suspended animation, joking that she didn't think her great-great-great-great-great grandchildren would have to worry about him becoming mobile again. (StH: #167)

Background information
It is currently unknown why Shadow decided to take over Mobius, as he has never showed any signs of wanting to conquer it. However, it is possible that due to Sonic's absence from the timeline, his attitude would never have changed to a more positive alignment, and thus would attempt to reshape the world as he saw fit.