Itachi likely only got the totsuka to deal with Orochimaru. It hasn't been explicitly stated in canon, but it seems like Itachi figured out Orochimaru would takeover Sasukes body, so he wanted to deal with that. Where he found it is kind of.....

Then presumably, he would have used Izanami as a plan against Obtio, after knowing Obito wanted the dead Uchihas Sharingan for Izanagi spam, with Obito pointing out he's lucky that Itachi didn't know he was a full on larper as well, making Izanami diff even worse.
These would be his best moves in general, he used them to take out Orochi/Kabuto before he died. Tbh, something like Ameratsu is a meme in my mind, since it never actually takes anyone out, except like fodder.