Even though I give the JLA the majority wins, the Eternals make them work for it, HARD.
Every single one of the Eternals
a) has complete control over their body down to the molecular level (good luck killing one)
b) telepathic/telekinetic powers that vary depending on skill level (good luck mindraping them)
c) can teleport (good luck entrapping or BFRing them)
I'm not sure on the rules for the Uni-mind formation but if Ikaris is the Prime Eternal version, he can initiate a Uni-mind, then the JLA is fugged.