Sigma is an evil genius who also builds robots to try to kill Megaman X. But he also builds stronger robots called X hunters. He appears in the games megaman X1 trough X6. He's also VERY hard to beat in most X games. He kiddnaps Zero in X6 and megaman has to find him. Also he has gotten Dr.Doppler to try to kill Megaman but of course doesnt kill him.
