The weakes point in rainbow decks are:
+quanta stock
+card drawing
+build up
That said, most effectives decks against rainbow are the ones that messes with you quanta (black holes, gravity nymbhs); and the ones that build up a lot faster than rainbows (usually upped mono or duo decks, like fire rush, graboid shrieker, life rush); and the ones that shut downs (deflagration [fire], destroy [gravity or entropy]).
There only alternative is a speedbow deck, but those lack of control cards (pulverizers, deflagration, oughtys, etc)