im repeating what ive seen people saying the boss is designed to destroy "normal" builds. i could do it without the great shield, i/e a normal shield most people doing it with great shield and use a spear ditching there "normal" game build swapping to high arcane etc, where as i was using great shield and great sword. which is the way I've run through the whole game and no stat swap to arcane.
just pointing out the boss is completely doable without changing your build to Greenshields, spear and rot/bleed him to death... which is not a "normal" build for running though Elden ring for the most part if you base normal on youtubers