Personally, I Think its the IE, but I am not sure. After all, they imprisoned The World Razer (read the codex from Belsavis, end of a long questchain). And, if you look at SOA's force powers, its clear they are powerfull. But please post your opinion/answer.

Infinite Empire by a very large margin, as powerful as Sidious was, that power simply cannot win him a galactic war, especially when almost all rakatans were immensely powerful themselves, perhaps even more powerful than Sidious was, he might have been the Strongest Sith ever, but nowhere does it state Dark Side practitioner ever.

Oh, ok. Now I love that decease (sp?) that almost wiped the Rakata out. But, if it was Luke Skywalker against, lets say SOA, I think Luke would win, because in the end, the light side is the one that stand Victorius. But thanks for reply!

We don't even know everything about the Infinite Empire, but what we do know basically says that the only reason they ever fell is because of the disease. They were kinda like the Eldar of Star Wars (MUCH less advanced) in that basically, if they wanted something it happened. At least the ones that weren't slaves.