Avengers #22

The "Ultron Unlimited" arc reaches its fourth chapter with a cover that says it all: a gleaming, menacing Ultron looms center stage, his chest reactor blazing, while the scattered, defeated forms of Earth's Mightiest Heroes — including what appear to be Scarlet Witch, Thor, and a host of teammates — lie strewn around him in a blood-red tableau. George Pérez's linework crackles with grim energy, packing the composition with fallen Avengers to drive home just how overwhelming this robotic threat has become. Kurt Busiek's run on the title was delivering some of its most dramatic moments in 1999, and this cover makes a compelling case that "Ultron Unlimited" belongs among them.