Board Thread:Naruto Discussions/@comment-25516007-20141008201906/@comment-25382671-20141009142134

ItachiWasAHero wrote: Obito praised Nagato as the strongest, he made it clear he did not want to fuck with Itachi, and he also made it clear that it would be a dangerous mistake to bring back Jiraiya and Shisui even with Edo Tensei, telling Kabuto not to push his luck.. mind you he already saw Madara's edo tensei.. and he STILL said that. So It is clear that Itachi, Jiraiya, Shisui and Nagato are 4 people Obito would rather never have to deal or dealt with. This is a really good analysis. Itachi, Shisui, Nagato and Jiraiya are four shinobi who are among the strongest.

In no specific order, they are (but not limited to)

The Kages, obviously. Itachi, Naruto, Kakashi, Sasuke, Nagato, Madara, Obito, Jiraiya, Guy, Darui, Orochimaru, Shisui, the Akatsuki members, the Jinchuuriki.

I believe that fights among any of those would be much more about being able to counter-attack and read the enemy correctly than by using skill alone.