OK, Shepard did every option right, he purchased all the DLC and everyone is happy. As a result, everyone is in the fleet. Asari, Turians, Geth, Humans, Quarian...everybody. They give the signal and everyone jumps. There is a dimensional rip, and the end up materializing right at the Covenant's doorstep right after Truth ascended to power, but before the war with humanity. Both sides are at the height of power. The battle is joined as a grunt accidentally trips and lands on the fire control of a plasma launcher. Who wins?