Titan Metal Sonic is a creation of Eggman and a form of Metal Sonic.
The original was made by Robotnik and used against the Chaotix but was defeated by Giant Knuckles.
The Ultimate version was finally completed by Eggman and used to attack New Mobotropolis, it almost destroyed the city and proved to be almost invulnerable, taking a blast from the Death Egg along with some Ixian Magick to defeat it.
Titan Metal Sonic is seen being rebuilt in the Death Egg, it is later completed and upgraded into the Krudzu Titan Metal Sonic.
The robot was also capable of flight.
Titan Metal Sonic v1-Knuckles' Chaotix Special
Titan Metal Sonic v2-Sonic the Hedgehog 231
Titan Metal Sonic v3-Cameo in Sonic Universe 37, Upgraded with Krudzu Hybrid Hydra in Sonic the Hedgehog 241