One bloodlust Trench vs one bloodlust Xenomorph, battle to the death! (Trench is aware of the acid blood, but how much that element will affect the battle outcome is up to you, dear comicviners, to determine :-) )
ROUND 1: on the deck of helicarrier on a dark stormy night, 20 feet apart.
ROUND 2: In the water, . 20 feet apart. (Xenomorph could swim and did have underwater feats BTW).