Lore wise... Does Tsukuyomi/KotoAmatsuki even work on another fully matured cheatagon? Or any matured ocular power for that matter? I know most ocular powers come with built in genjutsu resistance- Aside from avoiding eye contact... What would happen if two equal similar level eye cheats get into a genjutsu contest? The one with higher will or mastery wins? They both fizzle out and need to have a physical showdown?
Izanagi: allows reversal of reality over a short period of time. Famously used by Danzo as a “free life”, reversing his death. Izanami: Can be used to brainwash someone to accept a predetermined “fate.” Kotoamatsukami: most powerful genjutsu in history. It can rewrite someone’s memories so well, giving them experiences to conform to a single command. If Shisui gave the command, “Be loyal to Konoha”, it may give experiences that the Hokage raised him as a child and taught him the will of fire and he had many loving experiences in the village. With all that being said…why are you afraid of Izanagi? It’s not really a threat if you destroy the body completely and make sure they’re dead and not reversing reality.