This is the armored Hal Jordan green lantern who battled Mongul in the Reign of the Supermen storyline.
The hammer is the one used by Steel. Too bad for McFarlane toys, whenever they make long weapons such as this and staffs and swords, they are made of soft material which bends and never stays straight. They never corrected that error.
Still, even without the hammer, the figure is amazing and worth collecting.