Titan Metal Sonic

Titan Metal Sonic is a robot created by Dr. Eggman. Originally an upgrade-form for Metal Sonic v2.0 (and was destroyed easily by Knuckles), Titan Metal Sonic is a regular robot Eggman has used ever since Operation: Clean Sweep.

Metal Sonic v2.0 Upgrade
When Renfield the Rodent had opened a carnival on Angel Island, Knuckles and the Chaotix–Vector, Espio, Charmy, Mighty, Ray, Heavy, and Bomb– went to save the Freedom Fighters from the evil Doctor Eggman. However, Eggman left, only leaving a new Metal Sonic. The robot clearly knew he was outnumbered, so he used his Power Gem to upgrade himself to Titan Metal Sonic. Heavy gave his own Power Gem to Knuckles, which caused the echidna to grow into the same size as Titan Metal Sonic. The robot was defeated easily. (KCX)

New Mobotropolis Attack
By 3237, Eggman had made "Project: TITAN," which actually turned out to be Titan Metal Sonic. He used it to destroy New Mobotropolis, which was sent out from the newly builted Death Egg, along with Project: Deadly Cuddles. With Sonic distracted by his roboticized love, Titan Metal Sonic was destorying the city up until Bunnie and Ixis Naugus decided to help. Naugus had crystallize both Titan Metal Sonic and Bunnie in order to save New Mobotropolis, where he would later be crowned king. (StH #231, #232)

Combining with a Forgotten-Foe
Briefly shown before Eggman attacked Central City, a Titan Metal Sonic head was shown in the production during Snively's escape. (SU #37)

Later on, when Team Fighters– Sonic, Tails, Amy, and T-Pup– were chasing the Death Egg before it got to Albion during its invasion, Eggman had found a seed of the long-forgotten-Krudzu. He combined it with a new-previously-unused Titan Metal Sonic. He sent out the robot-Krudzu-hybrid to distract Team Fighters. It was defeated easily by the heroes. However, the Krudzu managed to get a hold of an offline-Metal Knuckles. (StH #241, #244)

Trivia

 * It is obviously based off of Metal Sonic Kai.