This would be great to watch, but I think it will have to come down on how many Xenomorphs and what kinds are fighting him. If there are like, 4 normal alien and 2 predalien, then the thing wouldn't stnd a chance (Considering how xenomorphs learn how there opponents work when they are fighting it)
Hmmm... hard to say. Considering that the thing is an all assimilating organisim where all of its cells make desicions for themselves, and that it is almost impossible to destroy, does throw the battle into its favor. But, considering the xenomorph's intelligence, it could figure out the thing's weakness: corrosive liquids( such as the xenomorph's blood), or fire. If the xenomorph wounds itself trying to escape or deliberatleys wonds itself, the pressurized acid would spray a great distance, which could turn the tables in favor of the xenormorph. Also, xenomorph packs can coordinate attacks, and they learn quickly. Still, the debate continues.........
The xeno wins easily since it has acid as blood and genes which would kill the things cells if it tried to copy it, and in a fight I´m sure the xeno could kill it as well pretty easily.