The Reapers are capable of cleansing the entire galaxy of sentient life with complete ease. They are massive (multiple kilometres high) and their on-board weaponry alone is exceedingly powerful. As for their numbers, well no-one knows exactly, but I got the impression that there were an almost limitless number of them. Sovereign (a reaper that spoke to Shepard) said that their "numbers would darken the skies of every world." So at the very least, there would be millions of them. We're forgetting that the reapers can control nearby minds, and if they can get into contact, they can transform other sentient life into husks to do their bidding. But man, the Imperium has over a million planets of far, far more advanced beings than any of the ME races. 38,000 years more advanced. And they're very militaristic. It would take the Imperium virtually no effort whatsoever to dispose of the normal ME races. It depends on the true numbers of the reapers, and whether or not they are actually limitless in number. But within reason, I think the Imperium wins this one pretty easily. Even a million reapers could be easily accounted for when you remember that it only took the Alliance fleet to take down a reaper (with plenty of survivours), and they were 38,000 years less advanced.
That the Reapers can take down an entire galaxy of species doesn't mean much in this case. The sentient speicies in question have based all of their tech on the Reapers' scraps. Not only that, the Reapers have a monopoly on the fastest mode of movement - the Mass Relays. All of the other modes of movement are significantly less effective. That the numbers of the Reapers can 'darken the skies of every world' doesn't actually mean much. So can the Imperium and the Imperium actually has more worlds to look over. The Reapers have significantly less resistence to fight and less worlds to conquer. And the Imperium can actually turn the dead to their side too. They are called servitors.
I already know pretty much everything you said there. You already mentioned most of it earlier, and I was explaining it further. You really make it sound like I'm arguing against you. I was weighing up the reapers, but tossed away any notion of them even competing against the Imperium when I considered the Imperium's technology, nature and numbers.
So, that's a unanimous prediction of victory on all fronts for the Imperium of Man. How about Reapers vs. Tau? That seems a little less like a curb-stomp battle.
Tau would snipe the hell out of them. Plus they have energy weapons, which would be even more curb-stompy.
That is slightly... foolish to ask. Its called science fiction for a reason. Some go to great lengths, some go to lesser. The fact of the matter is that, in the absence of any sort of real magic or supernatural power, people hold onto the hope that in the future, science and technology will be able to give humans supernatural abilities at will. Science fictions, in a way, opitimize that desire. And the idea of the universe having holes in their use of the law of physics actually makes no sense. The laws of physics are replaced in most science fictions with whatever is canon. The only time that you can apply the laws of physics is when there is an opening that is logical or contradiction in the canon. Surprisingly, most universes actually address the matter directly and inform people where exactly the laws of physics have been ignored. I would also assert, in response to Necron-Lord's post that there are indeed universes that are even more powerful and ridiculous than the Warhammer 40K universe. While I am not all that familiar with the vast majority of them, one must always remember that Warhammer 40K and Star Wars are both, in spite of their hype and technological advanceness, actually still confinded to single galaxies whereas other universes are in fact extra-galactic on varying levels.
