SM Naruto gave him a good match. KCM Naruto got negged by Nagato. Itachi defeated that specific Nagato. Nerfed Nagato>Pain.
I don't see how Pain is above Bee who has the 8 tails on his side and above Itachi.
Pain just fought an entire village, had to revive two of his paths, then blow that village up, his mostly powerful path was depowered at that time and Naruto had full intel on him, while he had none for Naruto.
Even with all that staked against him, He defeated Naruto. Just for Hinata show up and plot induced-Kurama awakening freed him. Then Pain managed to trap a 6 tails Kyuubi on Chibaku Tensei. Just for it to keep growing tails and Minato fix his seal so Naruto could start fighting again against a Nagato with almost zero chakra.
Pain >> Pain Arc SM Naruto.
Pain >> Itachi
Preta Path negate Amaterasu
Deva Path negate shurikenjutsu mastery
Rinnegan eyes negate sharingan genjutsu
Six paths gangbanging on you negates taijutsu mastery.
I love Itachi, but he shall know Pain.