Supreme Hunter

In an effort to subdue Alex Mercer, Dr. McMullen uses infection samples to concoct a new viral strain that will attack Mercer as a cancer. The cancer is injected into Mercer by Captain Cross during a battle, and the resulting tumor combines with Mercer's unique viral properties to form an intelligent parasite. With the help of Dr. Ragland, Mercer is able to remove the infection.

The parasite now forgotten, Mercer confronts Elizabeth Greene, and during their struggle, Mercer injects Greene with a serum derived in part from Mercer's cancerous cells. Though injured by the serum, Greene internally utilizes these weaponized cancer cells to form a new creature which she vomits out as a pool of liquid biomass. The pool contorts and grows into what eventually becomes the Supreme Hunter.

Inheriting properties from three parents - McMullen's cancer weapon, Mercer's viral strain, and Greene's own manipulation - the Supreme Hunter is capable of drastic regeneration, the copying of some of Mercer's abilities, and the command of the infected hive mind. Despite these strengths, the monster is defeated by Mercer. Wisely, it allows itself to be presumed dead and secretly regenerates from a small amount of tissue.

Later when a nuclear detonation sets to wipe out all life on Manhattan, the Supreme Hunter plans on consuming Mercer to provide the strength needed to survive the blast. Rather than again attack Mercer directly, it covertly consumes Captain Cross and assumes his form to get close to Mercer, but though it catches Mercer off guard, the attack fails, and Mercer defeats the monster for a second time, presumably permanently.