- A highly detrimental illness
- Stamina limits(likely caused by the illness)
- Chakra limits(likely caused by the illness)
- Sasuke
- Use of self-damaging techniques
The extent of his chakra and stamina, is still impressive. U_U
Itachi had his Susano'o activated for over an entire chapter after already exhausting himself. He was of course, terminally ill at the time as well. If you want the entire rundown on his chakra capacity, then read for yourself. It isn't by any means low.
Before his battle with Sasuke Itachi sent out two Karasu Bunshins [Crow Clones] to meet both Sasuke and Naruto [
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Itachi, not taking Sasuke serious yet, used genjutsu three times in a row as the fight commenced [
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Itachi then used another Karasu Bunshin [
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Used one his chakra taxing MS techniques, Tsukuyomi [
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Used the Katon: Gōkakyū no Jutsu [Fire Release: Grand Fireball technique] not once, but twice in a row [
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Itachi then proceeded to use his second MS technique, Amaterasu [
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] to only follow back up with using it again, in quite an alarming succession [
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] which practically lit up the entire Uchiha hideout [
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Shortly after straining himself by using Amaterasu twice in a row, Itachi is forced to throw up his third and final MS technique, Susano'o, in order to protect himself from the destructive power of Sasukes' Kirin [
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Itachi decided to throw up the final version of his susano'o armed with the two legendary weapons [
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]. Overall, Itachi had his Susano'o activated for more then an entire chapter before collapsing; which should stand for more or less 4-5 minutes.
And to top it all off, while Itachi had already overly exhausted himself, he still managed to use a transcription seal [fuinjutsu] and sealed away one last Amaterasu within Sasuke [
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It obviously pales in comparison to some other characters, but it is definitely not low. It can however, be considered a weakness given that most of his opponents usually have larger reserves of both.
1st weakness: He was solo king. He told Sasuke and Kabuto that because he was, sasuke ended up rogue.
2nd weakness: stamina. His disease decreased his chakra pool. But to be honest, his chakra isn't that high. I don't think he is stamina type. I would say without the disease, his stamina would be 3.5 instead of 2.5. His stamina should be around the same as Sauce man.