Foundation vs. Order? Dude, all they need are guns, some artillery support, wide area anti-thaumaturgic (anti-magic) arrays, and they're golden. Ever watched GATE? Think of it like that, but crank the curbstomp up to eleven in the Foundation's favor. And if the Chief God gets involved, it's just a simple matter of deploying reality anchors to prevent any form of divine intervention from reaching the battlefield.
Want to make it a fair fight? Have the Serpent's Hand go against the Order, instead. They're a loose group of magic-users and revolutionaries that wish to reveal the anomalous to the world and make it the new normal, as opposed to the Foundation's mission of secrecy and security.
Their feats, resources and numbers makes it less of a curbstomp, to be honest. Although their one advantage is that they have access to an infinite library that contain knowledge that was, will, and never be written. They only need to find the right books, and they'll have all the knowledge and intel that they need to beat the heroes.
But if you want to make it hilarious, have the Order go against Gamers Against Weed. Think about it: anomalous shitposters trolling the Order heroes for the M E M E S. Although they don't like getting unwanted attention and use their abilities and creations for murder, they'll most likely just resort to viciously elaborate pranks and ruin everyone's day.