Metallix

Metallix is a powerful form of either Metal Sonic or Mecha Sonic in the Sonic the Hedgehog series. The name "Metallix" was used in the British comic series Sonic the Comic, as a massive army of Metal Sonics called the Brotherhood of Metallix. Metallix himself was a large, red powerful Metal Sonic who ruled over them. However, in Super Mario Bros. Z, Metallix is instead the true form of Mecha Sonic, which is achieived by collecting the Chaos Emeralds. Alvin-Earthworm confirmed that Mecha Sonic would collect all 7 Emeralds before he cancelled the series.

Mario and Sonic: Worlds in Danger
Metallix (SMBZ) is confirmed to appear in Jmkrebs30's Flash series Mario and Sonic Worlds In Danger, this time as a fusion of Metal Sonic and Mecha Sonic. It is confirmed that Metal Sonic and Mecha Sonic will fuse into Metallix to battle Mario and Sonic the Hedgehog aboard the Death Egg sometime near the end of the series. This confirmed by the second intro.