#now: in a pitch-black environment the andalite would lose

[thejakeformerlyknownasprince]

Would an andalite be able to fight an xenomorph?

I'm going to say yes, for one key reason: andalites' tails can break the sound barrier. Alloran is described as cracking his tail like a bullwhip (#54). The end of Alloran's tail — i.e. the pointy part — would have to be moving at well over 700 MPH to make that sound. Xenomorphs, on the other hand, are described as moving at a "sprint that few Earth-based animals could have outrun" (X). That means at least one Earth animal can outrun a xenomorph. Since peregrines can't run, I assume the upper limit is with cheetahs, and thus xenomorphs' top speed is less than cheetahs' 70 MPH.

Obviously running speed isn't striking speed, but I'm not convinced xenos strike much faster than that — humans are able to dodge them, and they're not blurred when moving onscreen. So assume xenos top out at ~65 MPH, andalites at ~800 MPH. Alloran could probably dice up a xeno in the time one took to attempt one bite of him. Since Elfangor can tail-fight circles around Alloran (AC), it'd be no contest.

But I keep saying Alloran, and not Ax. Because AFAIK, we don't get mention of Ax's tail making that bullwhip sound. Ax is probably still faster than a xenomorph — Cassie notes his tail moves faster than a human eye can follow (#4), and Tobias realizes andalite tail-fighting is so fast a human mind can't follow (#33) — but he's slower than Alloran, since kid gets his butt kicked when he goes tail-to-tail with Visser Three (#18, etc). Ax takes on a friggin T. rex and wins (MM2), so he's no slouch, but he's the first to admit he's no Elfangor. So it might, somewhat, depend on the andalite.