but the protosses psionics as their base for technology, the closest thing that I have seen the combine with is what the advisors use, and that is just looks like the dark archon's maelstrom ability, which would be futile against those who are so in tune with psionics that they could take control of the advisors with ease, and the Nihilanth to the best of my knowledge is the only thing comes anywhere close to having the psionic powers that the protoss has, they have even come close to defeating. Now Imagine a race where every member is at that level, or stronger. In theory the combine wouldn't stand a chance, but then again the zerg forced them from their home world, but that was because of sheer numbers, not by any real technological advantages, (no offense to the zerg users out there, but by every thing that I have read about the zerg, they just can take hits, and replace their fallen quickly.) evolutional maybe, but not technological.
This is all "to the best of my knowledge" so if there any mistakes feel free to correct me, but please don't be an ass about it plus the Combine would obviously win.
That may be true, but Gordon Freeman single handedly defeated the Nihilanth so (keeping in mind that the Combine defeated the human race in a matter of hours) just think what the ENTIRE COMBINE EMPIRE could do