Itachi is a poorly written mary sue who's sole existence in the manga is as a plot device for Sasuke. He is also, by the way irrelevant and these redundant hyping threads need to stop.
He was a selfish, abusive, manipulative, arrogant, hypocrite. None of his plans worked, and the only reason things didn't completely blow up in his face is because of the unforeseeable circumstances. Everything he touched turned to crap. He was also the world's worst spy and older brother.
Itachi admitted inferiority to Tobi, whom he thought was a weakened Madara, and even then didn't know how powerful Tobi really was. Itachi also admitted equality with Jiraiya, whom is also below Tobi. Madara is the Uchiha god.