Sigma, is a CAW Legend in ACWL (One Time World Champion), he is a video game character; who is the main antagonist of the Mega Man X video game series. He serves as the final boss in all games except Mega Man X: Command Mission and Mega Man X8 (in the former, he makes no appearances and in the latter, Sigma is the penultimate boss). Created by Dr. Cain, Sigma was considered the finest of the Reploids and was the first leader of the Maverick Hunters, peace-keeping androids who defend humans against their renegade counterparts. Although he was once honorable, Sigma unexpectedly goes berserk during Mega Man X and rebels against humankind (the cause of this was later revealed to be coming in contact with the Maverick Virus). He defects to the Mavericks and assumes the role of their leader.
Sigma appears as a tall, bald humanoid in most of his forms. Although he has been destroyed countless times, Sigma's programming always survives and builds himself a new form, ready to menace the world once again. It is implied that he grows more insane with each transformation. His primary enemies are X and Zero.
The Maverick logo is actually a stylized version of the Greek letter Sigma. The symbol for Sigma, "Σ", looks similar to a capital "W" turned at a 90° angle; the letter W is the insignia of Dr. Wily. This does not necessarily mean the logo is a reference to Wily; it might be a reference to how the symbol itself is often used as a symbol for villains of the Mega Man series in general.