Rules for this match-up:- Pein can only use Yahiko's body, the Summoning body (the one that looks like Deidara), and the fat body that absorbs jutsu. Don't go "Pein will win because he can use more bodies". However, he starts with all three of these bodies already deployed.
- Pein has full knowledge of Kakuzu's and Sasori's abilities and basic techniques. Kakuzu and Sasori also possess knowledge of Pein's general fighting style, no specifics though.
- Kakuzu has all his five hearts. Sasori starts in Hiruko puppet and can deploy the Sandaime Kazekage puppet, however, he cannot use his true form or the rest of his puppets.
- Do not start assuming that Rin'negan is the greatest thing since Jesus. Pein's abilities are restricted to what we've seen, with any logical additions (eg, different Fuuton jutsu etc). Same goes for Kakuzu's jutsu.
- Pein has a limited way to negate Sasori's poison. Let's say he has the same antidote that Sakura had, three doses.
Feel free to speculate what would happen if some of these rules changed, for example, if Pein had more antidote / could use more bodies, if Sasori could use all his puppets etc.