G (Resident Evil 2)

The first mutation of the creature known as G, formally William Birkin.

In this form he still partly resembles his former self. The main characteristic is its overly large arm. This was due to the G-Virus overcompensating for a specific injury and mutating in an uncontrolled fashion, in this case it was the bullet-riddled arm when Birkin was shot by the Umbrella forces coming to steal his research. Additionally, the G-Virus has one consistent mutation pattern in all the hosts it infects, and that is the presence of a large eye, presumably its own method of vision at this stage.

When you do battle against it, it is best to avoid that large arm by keeping a good distance between yourself and the large metal pipe it holds as a weapon. Unload a barrage of weapon fire from either your Enhanced Shotgun or the Grenade Launcher and it will fall to its knees in no time.