E-123 Omega is the last of the E-100 series robots created by Dr. Eggman. Due to him abandoning the project, Omega felt betrayed, and rebeled against his creator our of revenge. He teamed up with Shadow the Hedgehog and Rouge the Bat, and the 3 have been close friends ever since. Omega loves destruction and battling, to the point of being egotistical in his own abilities. He thinks little of others that aren't Shadow and Rouge, though he does have a respect for his former robot comrades, especially his "Older Brothers". One of those Older Brothers was E-102 Gamma, who, while not the first to gain emotions and rebel against Eggman, was the first to turn good as a result of seeing his brothers die, having to fight those who remained, and ultimately sacrificing himself in the process. Gamma is far more noble than Omega, and while Gamma's brothers' personalities are unknown, they lacked free will and were merely tools for Dr. Eggman

While there is no specific voice I want for these roles, they all basically sound the same. He was voiced by John St. John in the originals and Vic Mignogna currently, however the filter is heavy enough that you can't tell the difference. Regardless, here is a voice example:

https://www.youtube.com/watch?v=VtN4lhWl1Bk