I have to disagree. Nagato is basically invincible except to taijutsu and sealing jutsus, and his abilities make both of those difficult to utilize:
Shinra Tensei is particularly haxxed and has somewhat poorly defined feats, along with the ultra hax Chou Shinra Tensei and Chibaku Tensei which are both able to obliterate entire villages.
Then there's his cyborg abilities increasing his strength and offense, lasers that can destroy buildings and such. Not to mention additional faces and a greater range of vision.
The ability to kill you with just a touch.
The ability to absorb virtually any jutsu, with no defined limits to such ability.
Not to mention a summon army.
Summons including Gedo Mazo, the towering shell of Juubi that can smash through villages and eat souls.
Gedo Mazo spikes that can control other living things, which are especially effective on the dead which allows Nagato to be six people simultaneously, giving him the numbers advantage and superb teamwork.
And although he can only resurrect the living one time, it can reconstruct the dead repeatedly which makes Pein hard to stop.
Naruto needed Sage Mode to fight him, and the power-levels have only increased since then.