Well, if you look from the other side, Barney survived the black mesa incident, the seven-hour war, the occupation of the earth and lived and maybe even continues to live during the Combine. God knows what happened to him after episode 1. Gordon would have completely died in the Black Mesa if not for the gman, but he killed Gonarch, although as I heard he is quite tenacious, he killed Nihilanth (we know perfectly well who this is and what he is) and became a revolutionary in city 17 and in my opinion for the locals he is “immortal” there. I haven’t played Opposing force until the end, but I know for sure that he sent race X to hell (all I know)
I love the shift theres been in the last couple years there's been on how people perceive the Combine, before they felt like just cannon fodder to shoot at just for the sake of killing, in recent media, they look and act like real threats