Didn't play Elden but fucking hell genichiro was something else. I also think the game clearly peaked there..
Balteus was also no fucking joke as well and unlike Sekiro the whole game is amazing despite getting significantly easier from that point, because you soon get the pilebunker and other stuff.
The thing is for Balteus you could probably cheese it with a tank build (I went max lightweight/speed which left no room for error) but for Genichiro there's no such thing you had to learn the DDR sheet or die.
So Genichiro wins in term of having to git gud, still Balteus difficulty was less artificial (even before they nerfed it) because AC6's bosses never feels cheap or hardcore memorization slop based and I prefered AC6 easily as a game overall.