That's not much of a challenge I'd say. Spawns self aware and hyper-reflexed suit would chop up any alien trying to get close. And even when it comes to melee combat, Spawn can sustain more damage, dishes out even more and has regenerative powers. The alien is chanceless.
And hey! How can you be behind me too? Is this one of those damn space/time continuum anomalies again? That's gonna leave a hell of a hangover...
Hmm, better! Still I think Spawn will be able to cripple her from a distance, jump on her back and unleash the spikes, sustaining some acid burns maybe but I think he'll 'live'. Or just jump by her and chop her head off in mid air, after pulling a leg or 2 off. If she could get close and grab him, he would be in trouble with the whole headbiting issue... But Spawn is faster and has more methods of attacking.
He might even be able to just burst right trough her (yeah biatch, see how that feels for yourself!), but then he may be exposed to too much acid.
Versus the Queen is a better match, but aliens are still relatively fragile compared to Spawn.