Cool idea! Maybe people should quote and edit the below with their views (adding more as the list grows) so the list isn't lost.
Ellimist/Crayak vs The living tribunal (marvel)/ Spectre (DC)
Winner = Living Tribunal
Omnipotence across multiverse. Ellimist/Crayak has only been shown to manipulate space in this universe and across time.
Andalite/ Hork-Bajir vs Xenomorph (only seems fair)
Winner = Xenomorph
Explained in the other thread!
Chee vs The Terminator (T-850)
Winner = Chee
Hang on are we talking about defeating (incl disable/render harmless optional killing?) If it's to the death and the Chee considers the Terminator a species (so violates it's non-violence restriction) then the Terminator would tear the Chee apart ... eventually.
Anyway the Chee might not consider the Terminator an intelligent species. That model has a chip preventing learning. This also means the Chee would outsmart the Terminator. Without the chip, I'll still go with the Chee from their millenia+ of experience.
Holograph tech might not fool the T-850 so there's no point discussing that.
Vehicles have been seem to damage that model of Terminator but the Chee might have been able to withstand a collision better so they seem a bit more durable.
Howler vs Predator
Winner = Howler
If they're both armed with equally powerful weapons then I'd go with Howler. If they're unarmed I'd probably still go with Howler. Howler howl (obviously) and their ability to see vital organs would be helpful. Not to mention their collective memory means they have experience from millions of warriors.
Yeerk vs Goa'uld
Winner = Goa'uld
Without hosts they're both pretty harmless but the Goa'uld can probably survive 3 days without rare Kandrona.
With hosts, Goa'uld strengthen their hosts which Yeerks don't.
Not so sure about the predator vs howler. I mean if a howler is decapitated, it dies right (based on Rachel prepared to kill jake if he lost control over the morph) ? And predator has all this stealth technology and sharp stuff right, decapitation for the win. At leat if this is in a city or jungle, in a cege the howler stomps.
And Chee vs terminator. The chee would have his anti-violence programm. But I don´t know which is more durable or strong.
I agree on everything else.
And I´ll put this up just because I´m a green lantern nerd. (I´m not actually expecting people to debate)
-Green lantern vs yeerk battle fleet (pool ship + 50 bug fighters)
(actually it doesn´t matter how many ships you thro at it)
EDIT: I planned to post a link to a video showing my point, but youtube hates me today, I´ll post a facebook link if I can.
EDIT 2: Youtube worked finally today, so here´s the link
AVRA IS A BADASS/ the true power of a lantern