Sigma.

About Sigma

Sigma is a fictional character and the main antagonist of the Mega Man X video game series. Created by Dr. Cain, Sigma was considered the finest of the Reploids and was the first leader of the Maverick Hunters, peacekeeping androids who defend humans against their renegade counterparts. Although he was once respectable, Sigma unexpectedly goes berserk during Mega Man X and rebels against humankind after coming into contact with the Maverick Virus. He defects to the Mavericks and assumes the role of their leader. Due to the virus integrated into his circuits, he can survive seemingly anything, and constantly returns to menace the world.