You cannot go up against the structurally most perfect, most lethal, living organism in known existence.
In space, for some odd reason, they cannot be killed, period.
The reason the Resurrection aliens were able to be killed as their Human DNA. As seen in ALIEN, the original, they through everything they had at that thing (including blasting the damn thing with jets powerful enough to send a ship flying all the way through space) and its body was still INTACT.
Seriously, no matter if you're the goddamn Master Chief or the goddamn Batman, you are NOT killing this f**king thing if it is in space.
(Hell, even SUPERMAN needs sunlight to function properly, he would die as well.)