Well izanami is a super strong genjutsu . Tsukiyami or however its spelled is an alll powerful eye technique genjetsu but has to make eye contact. Itachi can make his last as long as he chooses since he controls the time of it. Izanagi requires Senju blood or dna and it was also considered the ultimate illusion
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. So why didnt danzou use this on sasuke or why didnt Tobi use this on the girl. Tobi didnt think the girl from the rain village had a technique that can actually defeat him so he had to use hiis free life izanagi. Danzou didnt want sasuke in a genjutsu he wantedf him dead plus tobi couldve came and took sasuke and dispelled the genjutsu at the hideout.
So wats the difference ?
izanami doesnt require senju blood. But you need to be near the person your going to use it on them and some time to prepare a loop scenario.
Izanagi is more like a free life. Like a restart if your playing video games from the last save point. So you cast it ready and attack all out and the moment u get hit with a super attack you restart.
Itachi if he had a real body he wouldve died and not pulled it off. So izanami was perfect for his healing puppet body.
Another few things i feel like the reason why Orochimaru went bad is because of Danzou. I feel he learned from his evil ways and was fine with it.
Also i dont get how Danzou or Kakashi couldnt dodge Sasuke's susanno. One got saved cause of izanagi and kakashi said it himself he had to use his Sharingan. Pain was catching up to the speed of cloaked kyuubi forms and couldnt dodge Itachi's susanno ( fine it came outta the smoke ) but Kabuto was dodging them fine in my opinion. I hope naruto doesnt have any trouble doing the same.