Fear Agent, Vol. 1: Re-Ignition by Rick Remender

When down and out alien exterminator, Heath Huston stumbles upon an extraterrestrial legion of amoebas preparing to annihilate the Earth, he's forced to choose between the bottle and resuming his roll as a peace keeper, as The Last Fear Agent. Heath's former band of soldiers, the Fear Agents was comprised of a group of the last remaining humans on Earth, whose sworn duty was the protection of their home world against alien invaders. A number of years after preventing a large scale invasion of Earth, the Fear Agents were all slaughtered in a mysterious incident.