AMATERASU
People always say that Itachi can only use 2-3 amaterasu. What is often overlooked, is the amount of amaterasu Itachi used in his fight with Sasuke. He managed to engulf half of the forest surrounding the building [
You must be registered for see links
] - [
You must be registered for see links
] - [
You must be registered for see links
]. Those pages are in order by the way. Prior to that, he used an amaterasu of this scale [
You must be registered for see links
]. Then he extinguished it [
You must be registered for see links
]. He later proves it's well within his capability to control the quantity [
You must be registered for see links
]. Check out the amount Sasuke is releasing[
You must be registered for see links
]. Itachi could
at least produce ten of those.
Also keep in mind he used the Tsukyomi earlier, as well as a few other jutsu.
SUSANO'O
Susano'o is a materialization of the users chakra, but how can it materialize if the user has little to no chakra left? Itachi, while he was near death, managed to manifest his Susano's complete form. Not to mention, his body was very weak at that time; due to the disease. This actually speaks volumes of Itachi's chakra control/levels; especially since most brush him off as a guy who can't hold out for very long. Yet, he was able to materiliaze his chakra on this level [
You must be registered for see links
] - [
You must be registered for see links
] after performing very chakra-taxing jutsu and even outlasted Sasuke.
Susano'o users can even partially manifest susano'o; presenting simple ribs for protection
You must be registered for see links
. If Itachi really wanted to, he could even start a battle wearing a simple cloak and still get pretty far before tiring [
You must be registered for see links
], pay close attention to the first two panels. It would be less onerous on his body and chakra. As we saw, Madara managed to block attacks with a susano'o cloak (no bones or ribs) [
You must be registered for see links
]. That's basically all Itachi would need depending on his opponent; he could fight with that itty bitty cloak. As demonstrated above, his chakra levels and or control is certainly great enough for it.
He is also able to go on the offense/defense with Susano'o very fast. No Susano'o [
You must be registered for see links
] - [
You must be registered for see links
] - [
You must be registered for see links
]. As you can see, he managed to make a fist and extend it to protect sasuke,
at the last moment. I'm not surprised, since he managed to activate this [
You must be registered for see links
] before being struck by lightning. And yes this was real lightning, so there's no hyperbole here. If you're within in Itachi's range, he could activate his susano'o and smash you before your mind can process his actions.