Weakest to Strongest:
1. Zetsu - nothing really great about this character. He lacks power but he is good for intelligence and sneaking around. Pretty much the "ninja" of the Akatsuki who don't announce his presence to his enemies.
2. Hidan - His ability is unique and can be very devastating to many enemies who don't know anything about him. The only reason why he lost to Hidan is because he had days of intel on him and even made plans and traps on his defeat. Without that, Shika would have undoubtedly lost. The reason why Hidan is ranked this low is because he lacks intelligence and he is overconfident about his own power. He also fairs weaker than the others that are not mentioned yet. His power doesn't come from his attacks but from his resistance and immortal ability to tank blows from other opponents but people like Deidara or Nagato could easily just blow him up into pieces and call it a day because he has no type of strategy.
3. Konan - her explosive arsenal of paper puts her above Hidan. She has not shown much skill in speed or anything besides exploding things with paper. The only reason why she was able to pressure Obito so well was because she had planned that trap before he arrived. She even stated that she had waited for him and knew he would come. In the end she still lost. Konan has no type of skill besides turning into paper and disappearing into the wind.
4. Sasori - Sasori is definitely one of the dangerous members of the Akatsuki. His mastery in puppetry and his affluent purpose in poisons makes him very strong and unique. Many people believe that his battle with Chiyo and Sakura worked in the females favor but he was definitely nerfed in that battle and Sasori decided to lose in the end. Sakura was out of place in that battle and would have lost if Chiyo was never by her side to begin with. His Iron sand is one of the strongest of Suna and his many puppets of 100 army could easily take out many foes who lack speed or power. Sasori definitely fits this spot.
5. Kakuzu - this spot was iffy but I believe that Kakuzu fits here. His elemental advantages and linked with 5 hearts is his greatest asset so he could die 4 times and still live. He has great defense and offense and a much powerful flare of attacks that puts him above Sasori.
6. Kisame - This spot was the hardest for me as I'm not sure if Kismae should be here or Deidara, but I have concluded that since Deidara has his bird to gain air coverage which can avoid Kisame's water dome then Kisame deserves this rightful spot. Deidara is also a long range fighter which porves and even grater advantage against someone like Kisame. C4 can prove to be deadly which will prove fatal to someone without the Sharingan eye or any visual perception.
7. Deidara - and that is why I placed Deidara here from the above explanations. Kisame will have a hard time avoiding the bombs and tracking the Microscopic bombs. Deidara should out best Kisame in the long run.
8. Itachi - many fanboys would place Itachi above Pain but I feel that he should fit here. Chibaku Tensei will lift Susano'O in the air and give Pain the advantage to strike with almighty push or just extract his soul while he is distracted. Shinra Tensei will definitely push Susano'O back and give Itachi a little bit of struggle while the other 5 bodies gang up on Itachi and corner him. Since the bodies are linked sneak attacks will not work on Pain as shown with Jiraiya. All in all, Itachi is slightly weaker than Pain with 6 bodies.
9. Pain/ 6 bodies - As explained above Pain fairs stronger than Itachi and has the necessary fire power to stop Itachi's Susano'O and since Pain can absorb Amaterasu (As Kid Gamer has reminded me) Amaterasu will not be a threat but only to the summons.
10. Tobi/Obito - lastly we have the masked guy with the Sharingan eye. His ability allows him to warp anywhere he wants to. This can be useful in almost any situation and is one of the most haxed abilities in the manga. Itachi and Pain are not stopping someone that could just warp them into another space and then strike them. If Itachi activates Susano'O then Obito can easily warp behind Itachi and stab him with a Kunai or if Pain decides to use Chibaku Tensei, that isn't stopping him as he could warp out of the suction cup and land a fatal blow through Pain's head. Kamui is one of the strongest abilities and very few opponents can actually counter or stop it. Nagato and Itachi are helpless against it, thus Tobi or Obito is definitely ranked the strongest Akatsuki.