User blog comment:The Milkman/ME3 Predictions/@comment-1824113-20120215045410/@comment-211.30.44.215-20120216150647

A superweapon of some sort would probably be have to be employed - Reapers outnumber all the fleets of the galactic community combined, and they outgun them too. And let's not forget that during the scene of the Normandy fleeing Earth, we see the debris of the Alliance fleet falling towards Earth - obviously destroyed by the Reapers.