Sekiro guardian ape - Guardian Ape!!! : Sekiro

And you're right for sure, the boss designs force your playstyle in so many different directions while the game progresses.

Ive been stuck on this one boss longer then any other.

EDIT: keep a good amount of room behind you at all times to allow for easy retreat.

Have fun learning how to deflect his weird combos unless it's a sweep, then you jump , because after getting some deflects in, he will stand tall and straight and come down with a huge hit.

Immediately full charge the thrust type spear prosthetic and hit RT or whatever is bound to prosthetics again to do the armor strip mechanic against it's centipede, this will do huge posture damage and you can also combo it into a jumping forward ichimonji, which is faster than grounded.

Hit R1 right as his arm begins to lower to deflect this and stun him briefly.