The 3 Sannin

[Afro Thunda]

He didnt beat the whole country at the same time. He defeated Hanzou then killed off everyone associated to him in any way be it friends, family, that guy Hanzou bumped into off the street. He killed them all.

[DonMegaPLP]

Pein/Pain could easily beat all 3. Since Hanzou almost beat all 3 already ,and Pein/Pain killed Hanzou, I'm pretty sure he'd have no troubles.

True, but remember how long ago that fight with Hanzou took place. Pein defeated Hanzou recently which meant he probably wasnt at his "peak performance". He's supposed to be older than Jairaya, Orochimaru and Tsunade. At the moment they are in thier 50s. So I begs to reason Hanzou wasnt exactly a spring chicken during his bout with Pein. He was probably the same age as the Sandaime. Age does play factor at some point, as we saw during the 3rd's fight with Orochimaru... I think it was actually said outloud several times during the fight itself.

[Gaaraslostfriend]

If I remember right its because out of all their comrades they were they were the only ones who lived. Since they were strong enough to survie he gave em that name.