Rat Catcher by Andy Diggle
The Rat Catcher, peerless assassin, has finally slipped up - and one washed-up FBI agent has one last chance to hunt him down before he disappears forever. As the two men spiral in towards each other in a deadly game of cat-and-mouse across the badlands of West Texas, each of them hides a deadly secret from the other - a secret that could destroy them both.