Disclaimer: Nagato and [character] are ''stronger'' than Itachi. Please don't one-star my thread.
In a battle of minds, Itachi is unlikely to be outsmarted. With Sharingan insight and hailed as a prodigy that scored a 5 in intelligence, only someone with Shikamaru-level intellect and a Sharingan should be able to outsmart him, and Itachi should intellectually outperform or stalemate most others.The analysis made took a page,just a page.Despite getting to know a ''new'' dojutsu.Much, much better if you compare this with Sennin Mode Naruto vs Pain.
In terms of stamina: Itachi, while not diseased, is closer to Taka Sasuke, or perhaps his superior chakra control makes it seem so. When 17, he used some basic ninjutsu and genjutsu before splitting his chakra with an exploding bunshin, maintained a mind-control genjutsu on a girl, used Tsukuyomi twice, and Amaterasu once. He was fatigued at the end of the day, but nowhere near this condition in a time when Kakashi could only use 4 raitons in a day. Kisame knew he could have kept fighting if he wanted. Nevertheless, without using his three exhausting dōjutsu, his stamina is arguably a non-issue, even when sick.
In the field of genjutsu, Itachi can trick even visual-based geniuses in to suicide, and even combines throwing shuriken at enemy faces with his paralyzing illusions. If you know to avoid his eyes, he can put ninja under realistic genjutsu with a finger for several seconds until you realize it's an illusion. He can incapacitate genius genjutsu masters with torture illusions, can reflect even genjutsu masters' illusions, and can take control of multiple people from range. He can use crows to cast Sharingan genjutsu or deliver power.He is said to be able to control the Fox, which the databook states is the same power Sasuke used to control Manda.
When considering Itachi's ninjutsu, note that if you don’t have special training or powers like being a perfect jinchūriki, then you need to avoid his eyes and fingers for safety, making Itachi's ninjutsu nearly impossible to anticipate for most. Perhaps when utilizing Karasu bunshin faster than Hebi Sasuke could see, Itachi can overwhelm most individuals with very fast and very powerful fire releases. On water, he can surround ninja in drills including enemy blindspots so quickly that Kakashi, with a 4.5 in speed and a Sharingan, needed his 360° shield to block. Itachi can also throw up shields, which he used to block his exploding bunshin. Plus, to evade the exploding bunshin trick, you likely need a dōjutsu to see the internal chakra.
Similarly, when considering Itachi's taijutsu, remember that if you don’t have special training or powers like being a perfect jinchūriki, then you need to avoid his eyes and fingers for safety, making Itachi's taijutsu nearly impossible to anticipate for most. Itachi is fast enough to blitz Sharingan precognition and is sufficiently fast that he warned Killer Bee of his movements, with Killer Bee being one of the fastest characters in the manga. His taijutsu skill is also highly developed with his Sharingan precognition, as he engaged Naruto in taijutsu and then avoided Bee striking him from behind. Itachi's weapon skills are so advanced that Hebi Sasuke needed to summon weapons directly to his hands just to keep up, and Itachi even hurt Killer Bee with them. Itachi's hands are fast enough with these shuriken that ninja without top tier reflexes would believe that he's calmly holding shuriken while actually forming jutsu.
While the Mangekyō Sharingan makes all Sharingan genjutsu more powerful, Itachi perfected a special technique to break down an individual's mind in an instant. The potency of Tsukuyomi is dependent on the extent of time-manipulation, but Kisame was surprised that Kakashi was still alive, and Zetsu assumed that it made the victim unable to move. Naruto said that being hit by Tsukuyomi would finish off even Bee, someone with incredible durability and otherwise genjutsu-immunity. For most, looking at Itachi's eyes is an automatic loss. However:
If you don't look at his eyes, then reacting to Amaterasu is nearly impossible, because even the Raikage was tipped off by looking at Sasuke's eyes. Moreover, the Raikage spent time building bijuu sized chakra for his mega shunshin, which both Karin and C noted, but Itachi can activate Amaterasu mid-sprint while 5 meters away in a short amount of time. The heat of Itachi's Amaterasu was hot enough to burn extremely fire-resistant flesh: firebreathing toad innards and Sasuke's fire-blocking wing. Naruto also said this technique could potentially end Bee. However, this is not Itachi's ultimate jutsu.
Susano'o is not primarily defensive. The databook first and foremost hypes the perfect flawlessness in offense that surpasses Amaterasu and Tsukuyomi.The Susano'o possesses a jutsu which is said to be comparable to FRS and Tailed Beast Bomb. and it was arguably fast enough to catch Orochimaru by surprise between words despite being focused on. Kakashi and Danzō each had to use seal-less jutsu to deflect Susano'o attacks from 20+ meters away, and Sasuke hadn't even attained Itachi's level of Susano'o at the time. His Susano'o is among the best defensive jutsu in the manga, changing nature and shape to allegedly counter any jutsu, and Itachi showed that he can activate Susano'o in an instant for defense and thus offense.