Disaster is a robot built by Violet Blue.

He fights much like Mecha Sonic, but carries some arsenal built into him by Violet.

FYI: Eon, Flash, Violet Blue, and Disaster were all created with the Sonic Character Creation Generator on Newgrounds first before being drawn.

If you people are curious, though, the list of my personally made characters are as followed:

Good guys/Freedom Fighters:
Cheetor
Brave
Monquetta
CI-O-9
Sand Savior
Naziea
Sirus
Archon

Renegade Squad/Red's Team:
Red
Wolf
Strike
Canik
Razor
Dark
Tailmon
Oni
Blackstorm
Tallon
Foon-Ra

Bad guys/Dr. Robotnik's Badniks:
Panasa
Magno
Black Virus
Partisan
Prince Ricardo
Magnet
Sirocco
Fury
Omega Shogan
Geddon Arma
Monsoon

The Terrible Three:
Eon
Flash
Violet Blue
Disaster

Yes, I know the Terrible Three actually has four members, but their name comes from the siblings, Eon, Flash, and Violet Blue.