1. Kaguya
2. Madara
3. Naruto/Sasuke (with Bijuu)
4. Sasuke (with Bijuu)/Naruto
5. DMS Kakashi (Rikudo + Obito boost)
6. Juubito
7. Gai (8th gate)
8. Orochimaru (Hashi cells body, Edo Tensei, Perfect Clones, Shin, Mangekyou Sharingan)
9. DSM Kabuto (Edo Tensei)
10. SM Hashirama
Perfect clones? Shin? MS? Maybe I'm missing something on the first one, but Orochimaru doesn't have access to any of these directly. Unless we give him prep, but with prep, any Kage could technically have a fighting force of their own village. He's below SM Hashirama indefinitely, and arguably DSM Kabuto seeing as his Edo Tensei feats are restraining Tobirama. There's little indication to prove he can control a BM Minato, and we know he's unable to keep Hashi tied.
I'd put SM hashirama at eight, followed by Kabuto and then a Prime Orochimaru.
11. Nagato
12. Bee
13. Minato
14. Tobirama
15. Itachi
16. Muu
17. Onoki
Not the worst, I'd personally put Onoki above Muu though. Apart from his invisibility, Oonoki's got more impressive jinton feats, better doton, and generally more panel time.
18. Kisame
19. Jiraiya
20. Danzo
21. Mei
22. 3rd Raikage
23. Gaara
24. Gengetsu
25. A
Bit issues here.
Gaara needs to be much higher, I'd personally believe he is capable of defeating the likes of Jiraiya and or the Third Raikage. He's also, pound for pound, equals or greater than Kisame in terms of overall capabilities. SM Jiraiya is around the same, as well. I'd reorganize the list as the following.
My Pick said:
18: Gaara
19: Kisame
20 3rd Raikage/SM Jiraiya
21: SM Jiraiya/3rd Raikage
22: Danzo
23: Ay
24: Gengetsu
25: Mei
It's a bit sloppy, because numbers 18-21 are all in a very close level of strength. Bad match ups aside, I'd believe they share a general overall power with possibly Jiraiya lagging behind the rest. Danzo, aside from KA, is strong, I just don't see him being on the same level as those above. Ay could take Danzo's placement, I'm unsure of it all, but I'd think that it's a close match up.
Gengetsu is strong without intel, but again, full intel and an intelligent shinobi can come up with reasonable counters to his jutsu. Mei can't really beat any of the shinobi on the list. Possibly Gengetsu, or Ay if the fighting distance is large enough. But even then, he could outlast her and evade the hidden acidic mist.