Board Thread:Versus Debates/@comment-30426414-20161228222316/@comment-30426414-20161229180719

Ravenlot 27 wrote: Well, Itachi was going full-out with his chakra, he didn't spare hiself at all, since he knew it was the battle he's going to die in, and since we know that some amount of chakra is necessary to keep human alive in the Naruto universe, we can be completely sure that Itachi spent this amount as well.

If itachi spent that amount, he would be dead the first time he used susanoo and he definitely wouldn't be able to keep up a susanoo if he was running on the last of his reserves. This means that after sasuke ran out of chakra, itachi wasn't running on the last of his last reserves because he was able to keep using susanoo for a while. When pain defeated kakashi, kakashi was running on the last of his reserves and just by using 1 kamui, kakashi died. The point here is itachi's chakra outlasted sasuke's.

Yeah, Itachi used his MS techniques, but any of them was used only once + fireball and Sharingan genjutsu, while Sasuke was almost spamming his fireballs and chidori (though Chidori was the most taxing technique for him in part 1) + the same genjutsu, weapon summoning and high-level fire dragons. And Oro Substitution took a toll on his chakra too. So it's normal that they ran out of chakra almost simultaneously.

Itachi used shadow clones, 2 fireball jutsu, genjutsu, 2 amaterasu's, tsukuyomi, susanoo and amaterasu transcription seal. Compared to what sasuke used, itachi had more chakra consuming techniques and sasuke still ran out of chakra first.

Moreover, it was dangerous for Sasuke to spend all his chakra, since some of it suppressed Oro in his body, so after his Kirin usage, he still had some amount left, though he lost it attempting to get an additional power from CS to fight Susanoo Itachi.

When he used the dragon flame jutsu, sasuke said his next jutsu will end the fight but itachi noted that the sharingan can see chakra and he said sasuke was out of chakra (chapter 390 pg 18). This means that the amount of chakra sasuke was using to suppress orochimaru wasn't enough to even form another jutsu, while itachi still had enough to use susanoo.

Itachi had nothing to fear while using Susanoo, he realised he was going to die anyway.

Itachi had everything to fear while using susanoo, he wasn't free to dump the last of his reserves into susanoo because he had to make sure he had enough chakra to use the amaterasu transcription seal on sasuke before he died. Itachi didn't even die due to chakra exhaustion because tobi said he succumbed to his disease and thats why he died. Although we can be quite sure he was out of useable chakra when he passed away.