Obito, Nagato and Itachi. It is clear that the three of these cannot be defeated by Sakura. Nagato has Shinra Tensei to defend against Sakura's power as Obito has Kamui and Itachi has Susano'o. Nagato is extremely smart and Ningendo or Bansho Ten'nin can defeat Sakura basically. Kamui, Bijudama etc. is how Obito will defeat her and Amaterasu would "One Shot" Sakura. As will Tsukuyomi and a variety of other techniques in Itachi's arsenal.
Now let's look at the weaker end of the scale. Sakura could defeat Zetsu Pre-Yin Seal so I don't need to go over him. Hidan would get obliterated by Sakura's Yin Chakra Infused Punch. Hidan lacks the speed and the vitality to sustain the attack so he's done with as well. I will ignore Konan as we lack sufficient feats from her.
Mid-Level Akatsuki. They're easily the most disputed characters [in terms of ranking] in the whole series. Deidara cannot defeat her with C1, C2 or C3. The fact that Deidara is a long-distance, aerial fighter which limits what Sakura. C4 will defeat her without difficulty. In a fair one on one, Sakura will defeat Sasori. She has antidotes for his poisons and the brute strength and stamina to fight his various puppets effectively. You may argue that antidotes need preparation time...well poisons do too so we're either limiting both [Sakura would win by a long-shot in that case] or not limit either [Which Sakura will win with Mid-High Diff]. Kakuzu is disputable. He has the Earth Grudge Technique and has access to all 5 Basic Transformations. I think Sakura with brute strength can defeat Kakuzu however it is a flip a coin battle. Kakuzu can win due to his experience as a shinobi.
Sakura cannot defeat Kisame. He is clearly above Low Level Akatsuki [Hidan, Zetsu, Presumably Konan], Mid-Level Akatsuki [Kakuzu, Sasori, Deidara] but is beneath High-Tier Akatsuki [Itachi, Obito Nagato]. However he can compete with Itachi, the weakest of the High Tier. He can absorb all of Sakura's Chakra with Suiton: Daikōdan no Jutsu or Samehada. He possess the ability to use some of the largest Suiton Release techniques that we know and can easily overwhelm Sakura and defeat her.
To summarize, Sakura has no chance against Itachi, Kisame, Obito or Nagato. She can with Low-Mid Difficulty defeat Zetsu and Hidan as well as presumably Konan. She cannot defeat Deidara because of C4 but if that is limited she will eventually win and she will beat Sasori. She can beat Kakuzu but the battle can go either way.
Edit - Bolded my type. My mistake. I am following all the excess hype from Sakura btw.