That's an argument that was based off of a mistranslation:I don't understand how people are debating this. Obits himself was afraid of Itachi-_-
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Here is the actual VIZ scan:
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It can be interpreted now from this VIZ scan that Obito wasn't gonna attack Konoha while Itachi was alive due to his PROMISE to him, not due to Itachi being 100% able to stop him, as interpreted from the other scan.
Was Obito afraid of Itachi? Maybe. But Itachi was just as “afraid” of Obito as he was of him. It's safe to assume that in a fight, they would both be “afraid” of each other, because they both considered each other to be strong.