Infinite

"You may call me... Infinite... in the brief moments that remain to you."

- Infinite introducing himself to Sonic the Hedgehog.

"I am the tallest of mountains, I am the roughest of waves."

- Infinite's first lyrics in his theme song

Infinite is one of the two main antagonists of Sonic Forces alongside Dr. Eggman. He is a mysterious entity who assisted the doctor in his goal of world conquest.

Origin
Infinite was originally the leader of a mercenary team named "Squad Jackal" that was hired on by Dr. Eggman. However, after him and his team suffered a humiliating defeat from Shadow the Hedgehog, Infinite began seeking more power, eventually leading to him fusing with the Phantom Ruby.

Sonic Forces
Infinite assisted Dr. Eggman and his robots in an attack on a large urban center. After Sonic the Hedgehog fought off Eggman's forces, Infinite engaged the hedgehog and defeated and captured him.

Infinite later provided Dr. Eggman with a new power that allowed the Eggman Empire to conquer 99% of the world. He was later appointed leader of the Eggman Empire's military, and worked alongside the other members of it to enforce Eggman's rule.

Trivia

 * Infinite has many similarities to a previous Sonic villain, namely Mephiles the Dark. Both Mephiles and Infinite have a hatred for Shadow the Hedgehog with their goals to destroy everything as they both crave destruction. Both are powered up by something Omnipotent (Solaris's god powers for Mephiles, the Phantom Ruby for Infinite) and both of them have similar abilities. In addition Mephiles is making an Infinite sign in Sonic The Hedgehog 2006.