Big Daddy (Alpha Serie) 3D model

The Alpha Series refers to the prototypes of the Big Daddies. These were each stamped on a single Little Sister. A Big Daddy of the Alpha series has a higher free will than a later type. Since people who were also used for plasmid testing were first used for the Alpha series, these Big Daddies are able to use plasmids. The suit is lighter and allows greater mobility. In addition, the suit can be at least partially stored because the carriers are not connected to him. Remaining Alpha Series types, except Subject Delta, often carry machine guns, grenade launchers or shotguns. With their ties to their Little Sisters broken or broken, these Big Daddies are insane and attack anyone who encounters them.

Alpha Series types are featured in BioShock 2 and its DLC Minerva's Den.
(Wiki)