elite 342:

mine would be

covenant: arbiter fully upgraded rage and half upgraded scarab behind 30 fully upgraded hunters

unsc:cutter and spartens fully upgraded along with 29 scorpion tanks

 

with an army of these u cant fail unless the unsc uses its mac and the covenant have 20 locusts then ur screwed lol =)

you can not upgrade scarabs

for me it eould be anders + vultures