So Jiraiya was not the best teacher ever, was that really so surpsising?
Sasuke didn`t overhwelmed Deidara, he barely defeated him and merely survived because he was plot protected, i think at that point Kishi wanted Sasuke to be a big threat to Naruto, what better way to rank Sasuke up than by defeating Deidara?
Akatsuki members... Sasori had the disadvantage of fighting his grandma who knew most of his techniques and used her string to control Sakura, he still manage to fatally wound one of them, it`s also heavily implied (and i believe this to be true) that he actually let himself get killed.
Hidan: Succesfully defeated the Yugito and killed Asuma, Shikamaru simply outsmarted him because that`s what he does, he`s the smartest person in the show and possibly the whole ninja world, it was impossible to expect Hidan to win when Shikamaru knew all of his techniques and did some hardcore preparation.
Kakuzu: He took a small fleet of ninjas and got hit by Naruto`s OP technique.
Konnan: Pwned by fake Madara
I already adressed Deidara.
Kisame: Defeated the 5 and 8 tails, turned a fail into a win by making them believe he died and infiltrated Naruto and Bee`s hideout.
Itachi: Let himself get killed for Sasuke...
Zetsu is a freaking army. A. FREAKING. ARMY.
Yeah, pushovers alright.
Orochimaru: The other option was keeping him alive and have him turn into a caricature of a villian by frecuently trying to get Sasuke`s body, get defeated and escape with 1 hp claiming that this is only a minor setback. Oro was iconic yes, but he was weak, the other characters were growing exponentially while he simply did not, he needed to go, it took balls to kill him and i appreciate characters actually dying when they`re past their expiration date.