Izanami works, we know Loki does the tough guy with no feelings schtick based on his call with Mosa. It's pretty much just a vibe thing. Most OP characters play around and like getting hit, which obviously won't work against Itachi. Big Mom and Kaido are the easiest examples imo. Whatever your think on their respective PL's, we all know if he was on the rooftop it would end with them getting PTSD'd, as part of a gimmick where Itachi is always shown humbling egotistical characters. Which is why characters like Shanks, Katakuri etc are the only ones who'd likely win.
observation haki in general, is the perfect tool to fight a Genjutsu user, but we all know how optimal Oda is about it