Oh God. Here we go.
1) Itachi:
(list of opponents he defeated)
*Kakashi
*Orochimaru(twice)
*Nagato - That was Edo Itachi which was stronger than alive Itachi whereas Nagato was weaker than when he was alive. Also, Nagato would have owned Itachi if Itachi didn't have Naruto and Bee to destroy Chibaku Tensei for him.
*Sasuke
*Naruto - Naruto was not fighting with deadly purpose.
*Kabuto - Itachi would have been killed twice if not for Edo.
*Deidara - Fodder version.
2) Pain(nagato)
*Hanzo
*Jiraya
*Kakashi - Debatable. A bloodlusted Kakashi stomps Nagato since Nagato's mobility is crap. He isn't avoiding Kamui.
*Naruto
*Kiler Bee - Bee was not fighting seriously. A Bijuu Mode Bee stomps Nagato.
3) Naruto
*Gaara
*Kiba
*3rd Raikage - had intel.
*Neji
*Kakuzu
*Haku
*4th Raikage - battle of speed.
*5 Paths of Pain
*Deva Path
4) Sasuke
*Naruto - Naruto didn't fight with killing intent.
*Deidara - Deidara comitted suicide + Plot no jutsu
*Danzo - Danzo wasn't going all out/had KA on cooldown.
*Orochimaru - Oro was half dead.