Depends if you take the Kyuubi into concideration and if yes whether he can control it or not.
Naruto without the Kyuubi is of course strong, but far from unbeatable. There are numerous ninja who could beat him (Raikage, Killer Bee, Mizukage etc.).
If you count the Kyuubi in, but without him controlling it, not very much would be able to beat him. But because he doesn't have control over him, it could give an opening for the opponent.
If he has the Kyuubi under control, he's pretty much unbeatable.