Hold up, I think the monsters are approaching this from the wrong angle. “The end of the world” surely refers to an appocalypse-type situation where the planet and all its living inhabitants perish, right? Not a Will Smith in I am Legend set-up (minus the vampires) where all the living inhabitants of the planet EXCEPT for you and a friend of your choosing.
Ergo as this amigo is only needed for the brief period of time prior to your mutual deaths the attribute I would select is: possesor of an abundance of anti-anxiety meds. Practical!