Well Ottoman and Iroquois could easily be any civs nemisis. Their rush is so fast if performed correctly, not much can stop it. I have tried out nearly all the WOL civs and can't find anyone better at the rush. I would say Brazil are pretty good early game, just because of voluntarios, they may be able to even stop an ottoman rush, maybe iroqouis but that would be harder. I played some online 1vs1s recently, and Brazil is definitely a counter to Canada. Brazil have a good mass early on , Canada are too slow with the wood age up. This would also make Otto,Iroquois and Russia good counters to Canada too. Probably Inca too, though Inca coin bonus is op so they probably do well against a lot of civs.
Steam & ESO : CelticCrusader
I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.