Double

Double (ダブル) was a supporting character in Mega Man X4, as well as an antagonist. He quickly befriended during his mission, but as X began infiltrating the Final Weapon, Double revealed his true purpose; a spy sent by Sigma to infiltrate the Maverick Hunters. After slaughtering some Maverick Hunters in their headquarters, Double went after X inside the Final Weapon, and confronted him. He lost, and was destroyed.

As his name suggests, Double has two forms: the first is a short, overweight amicable form, but his second and true form is a much taller, thinner and stronger battle-ready Reploid, with sabers within the top of his hands and a gelatine-like substance is present in his body. Double's weakness is the Double Cyclone.