The Xindi killed 7 million people in one go,so why don't they just send more of the same ship/weapon to Earth and finish the job?
No reason to go all Empire, when a small little ship can do it. This is beginning to feel needlessly dragged out. It doesn't help that we have to listen to the council talk every episode. The Dominion and the Founders worked so well, because new information was given out over time.