Minato >>>Nagato even without BM mode. This is because contract seal >>Animal Path (can't summon ceberus etc, and if he already did, loses control over them), Asura Path (can't summon mechanical body parts, 'it was stated that he summons them), Outer Path (can't summon Gedo), Hell Realm (can't summon Hell demon or whatever that thing is).
Contract seal pawns all of those paths and leaves Nagato with only Preta and Deva (which is still OP). Now Nagato can pretty much pawn almost anyone with just these two paths so it can go either way from here on out. However, what if Nagato tries to absorb Minato's chakra and Minato activates sage mode? Obviously Nagato would turn into stone and die.
Still there are some unresolved issues, like does Nagato still have a 5 second cool down even when using the technique himself instead of through a corpse? If he doesn't, than he again is just too OP, but if he does, than that leaves room for the fastest and one of the smartest (if not the smartest) 1v1 strategists in the manga to exploit that gap.
Chibaku Tensei is easily teleported away, I mean this one aint even debateable. I rate this fight could go either way, but I'd give Minato 6 out of ten times.
Nagato>Itachi, not even debateable
BM Naruto >Nagato, I mean come on, preta just absorbs all that Chakra and uses it to replenish and heal Nagato. He's basically food for Nagato.
BSM Naruto on the other hand can beat Nagato, I'd also give him 6 out of 10.
Sasuke is no match for Nagato, period.
