Space is full of some weird scary crap man.
Arachnids: The Arachnid's monstrous appearance belies their cunning; for these are no mere beasts. They are conquerors bent on destroying all other species with an army of engineered evolutionary horrors. Many times have the forces of man been besieged by these creatures, and they are not always victorious. Whether bursting from the ground with some great leviathan-esque horror, or managing to sneak right past our defenses only to burst from within our own ranks, these creatures are as tricky as they are deadly.
Chimera: Hailing from an unknown planet in an unknown sector of the Universe, the Chimera's technology is about 60 million years ahead of mankind's. They come, monstrous in form but shockingly intelligent, with the sole mission of wiping mankind from the face of the planet. Lead by Chimera baring the rank of 'Angels', they corrupt humans through use of a virus, making them into Chimera hybrids which serve the Chimera war machine. Those that are not changed... are destroyed utterly without mercy.
Now these two monsters, constant threats to humanity that they are, will try killing each other for a change. Both will try overwhelming each other through sheer numbers. The Chimera will unleash their deadly virus, and the Arachnids will constantly be breeding new monsters for war. In the end, only one will be left standing. Only one monster can survive. So tell me, dear viewer...
WHO! IS! DEADLIEST!
(Disclaimer: Just to be clear, these two combatants were created / are owned by people far more creative / wealthier then me. I have made this, not for profit, but in the hopes of encouraging spirited discussion among fans. Please support the combatants official series. Thank you, that is all).