Sasori and Orochimaru high difficulty. Let's start with Sasori for one--One scratch and you're dead. One scratch means literally nothing to most shinobi and when Kisame or Itachi start off scratched one time it might not seem like a big deal until they're paralyzed a moment later and either Orochimaru or Sasori can easily kill them from that point. Kisame no doubt will be falling for this, he'll get touched once, Itachi it's arguable assuming he doesn't enter Susano'o the second the fight starts.
Plus, Sasori can just exploit Susano'o's weakness like the kages at the war did, Susano'o doesn't protect from below so all it takes is getting the sand underneath him which obviously isn't hard to do. And along with 100 puppets, a big enough AoE where neither of them should be able to get around he poses a huge threat. Not too mention, if Kisame uses large scale water techniques or even uses his water dome the poison could and/or would spread in the dome like Killer Bee's ink.
Second is Orochimaru who's backing up Sasori, this goes without saying. It'd make it far easier for Sasori to scratch them with their poison and Orochimaru is incredibly hax and powerful himself able to go pretty far in this fight against the 2 alone. Since Sasori has Orochimaru backing him up in the first place the fight becomes much more easy for Sasori to pull it off again for the reason that Orochimaru alone poses a threat, with Sasori there's not a doubt about it. Manda, Snake Summon spam, Oral Rebirth, Leech all Creation, Kusanagi, Triple Rashomon, etc. etc. etc.
Ok, I would have said inb4 genjutsu but it's obvious it would be brought up. Genjutsu won't do shit, Orochimaru never fell under genjutsu in a serious situation where he was fighting to kill, plus he has a 5 in genjutsu, guy was not trying to fight and trying to take Itachi's body, for ****s sake. Nobody understands this. And Sasori is a puppet with no nervous system, no idea how they're going to use Tsukuyomi on a heart or use that while there's 10,000 snakes, 100 puppets and a shitload of poisonous Iron Sand on the field to where they can't be touched 1 time or they're done for.
