Orochimaru; it's that obvious.
Though, this thread lacks a certain Minato.
I'd have given him the third spot if he were a poll option.
Obito at the second place, in my opinion.
He can easily phase through most attacks and, among other things, he has a storage of Sharingans in his hideout.
Plus, he can replace his limbs.
As for Hidan; he's not smart.
In fact he's a boiled egg.
In a one against one match it's just a matter of time when Hidan loses his cool and does something stupid.
That's why I don't give him a spot in my top three.
He's fourth, though.