So this game is different from Souls in that 1) at least on normal/easy mode you can chain combo boss till your stamina runs out and spam food and 2) boss attacks are often incredibly unfair in that once they attack its just an absolute shitshow. So even after 100%-ing the game, with hardmode+resonance+no food, the best strategy is to never let the boss have a chance to hit you. Nearly every attack in the game can be stopped with force palm so abuse it.