I'm not so sure on that one - in a purely physical confrontation, I suspect it would be a lot like the T-800 vs T-1000 fight in Terminator 2, with one of the combatants easily outmaneuvering the other through its ability to shape-shift. The T-800 won because it was able to out-think the T-1000 and use explosives against it; I doubt the Alien would have that kind of forethought.
Cutting and stabbing a Thing doesn't work because each piece is a whole, and it can just shape-shift to account for the physical damage anyway.
I'm sure an Alien would go berserk and rip the Thing up... I just don't think it would matter much. I'd think that, in a strictly physical match-up, without the Thing assimilating the Alien or whatever, at best they would destroy each other, and at worst the Thing would out-maneuver the Alien and create some way to puncture/constrict/crush the Alien to death.
If there Alien's acid blood also still works on TFAW, then it has even more of a fighting chance, but is still the underdog.
I’ve got 3 plausible scenarios, all depending on what is or is not in play. We can argue all day long as to what is or isn’t in play, but depending on what is, we have at least these options, take your own personal pick. Scenario1
If the Alien is not immune to infection, enough is said it becomes a TFAW as soon as it touches one:
Winner: TFAW by touching and thereby infecting the Alien. Scenario 2
: The Alien is immune to TFAW but its acid is useless (unlikely as the acid even burns through glass and industrial metals
), but in this case the Alien’s acid is compromised yet its immune system still fights off the TFAW virus nicely.
Winner: TFAW here, as it just has to become something in its history that can physically take on an Alien, or the little pieces of it that the Alien rips off eventually overcome the Alien. The T-1000 effect if you will.Scenario 3
: Alien is immune to infection and its acid blood is still in play. In the event where the Alien is immune to infection,then its Acid blood would also still be in play is what I consider more likely. In this Scenario the two are more evenly matched, or at least the Alien has an ok fighting chance.
Winner: 70% TFAW 30% Alien. In this event I still give it to TFAW most of the time, as the TFAW could end up in a lot of pieces. So many that if most of them are destroyed by the Alien acid, when they gang up on the Alien, there would still be at least one little piece left over. Even if it had to lose 99% of its matter to the Alien Acid to kill the Alien, it still has a surviving piece, and that makes it the winner.
If there was more than one Alien, several of them, then with their numbers they would have enough acid blood to more than dissolve the problem, and likely would still be at least one Alien alive remaining.