Eu até encontrei algumas coisas sobre Sasori ser o quarto membro mais poderoso da Akatsuki, mas não é nada oficial, apenas opiniões dos fãs, os mais trabalhados datam de 2011-12, não sei em qual parte o mangá se encontrava na época, talvez Kisame e Konan ainda não tivessem mostrado seus verdadeiros potenciais em batalha, ou então, essa onda tenha surgido por causa do péssimo aproveitamento do Sasori durante a guerra, o que pode ter irritado os fãs do personagem, DB4 não tinha lançado ainda também, então tudo o que tinham para argumentar era o mangá. Encontrei até alguns dizendo que Sasori era o segundo mais forte, atrás somente dos 6 Caminhos de Pain (KKK).
Vejam os argumentos do fã do Sasori sobre ele ser o quarto mais poderoso da Akatsuki
fan(boy) do Sasori na gringa escreveu:
This guy is extremely powerful, but very forgotten at the same time.
People hate on him because he lost to Chiyo and Sakura. First of all those two had cures to Sasori's poison and Chiyo was a skilled enough puppet master to dodge most of Sasori's needles. But none of that matter though because Sasori let himself die against them, just like Itachi with Sasuke.
So I'm going to break this down one-by-one.
Konan vs Sasori
Konan is also one of the few people who can evade Sasori's poison needles, but she still has to breath so poison fog would get her. She could escape that though, but Sasori still has to win. If she attacks with paper bombs Sasori simply uses 100 puppet show as shields, and attack with them at the same time. If Konan gets near Sasori, then Sasori would use his flamethrowers. Fire>Paper
Hidan vs Sasori
Sasori has no blood! Hidan can't get him with his scythe anyway because of the Third Kazekage. Sasori can easily have his way with Hidan with minimal effort. He can incapacitate him with Iron Sand Drizzle or Iron Sand Gathering Assault and then leave him to slowly die.
Deidara vs Sasori
Deidara himself said Sasori was better than him. Anyway Deidara isn't quick enough to avoid Prosthetic Arm Needles, and Iron sand is a more than effective defense against explosives. If Deidara gets airborne than Sasori can get him with Iron Sand World Method. He can also hunt Deidara down with Thousand Hands Manipulation Force.
Kisame vs Sasori
Sasori is Kisame's worst nightmare, since Sasori is long range and he attacks with tools, not chakra. Kisame cannot avoid Poison Fog or Poison Needles, and Performance of 100 Puppets would tear Kisame to shreds.
Sasori vs Kakuzu
This is the toughest fight for Sasori, but I think he takes this. Poison Needles are useless against Kakuzu, thanks to his Earth Skin. However Iron Sand would hurt Kakuzu along with Poison fog. Kakuzu still has his hearts, so Sasori would have to use 100 Puppet Show along with the Third Kazekage. They're perfect targets for Iron Sand World Method and Iron Sand Gathering Assault. Iron Sand is also a strong enough defense to withstand Kakuzu's collaboration techniques. Also Thousand Hands Manipulation Force would crush any one of Kakuzu's hearts. Sasori just has to many ways to defeat the hearts, and those are Kakuzu's strongest attacks.
Sasori's Databook rating is the highest of all those characters also, if that means anything.
Counterarguments are welcome!
https://animebase.me/threads/sasori-is-the-4th-strongest-akatsuki.219344/
Outro fan(boy) do Sasori
Sasori is a beast of a Shinobi and people do underrate him. I think he's the fourth strongest Akatsuki member behind Itachi, Madara, and Pain.
Obs.: Acho que com "Madara", ele quis dizer "Obito".
https://www.narutoforums.org/threads/sasori-is-insanely-strong.761750/