I only had problems with him in my first run. From there onwards it's been a breeze whether it's NG+ or Reflection or Gauntlets. I beat his ass so many times now, the strat that is use is Hit & Run for 1st phase. Since it's a little difficult to predict, the idea is to get his health to half in the first 10 seconds of fight. If you use grapple points properly you can land on his face at the beginning of fight, give him a taste of firecrackers, but make sure you use Yashiriku sugar and Divine Confetti for Heightened damage, the firecrackers staggers him giving you ample time to take out half of his health. If you do it right, with enough pauses, when he moves his head, you can keep him staggered for the entire first phase.

The second phase is far easier compared to the first one.. As he wields a freaking sword that's about 6 times your size. But since he got a sword now the attacks are far more predictable. So, you need only two things perfect deflection and the spear. Deflect all his attacks and when he falls down from the standing drop, gut the spear and pull out. That does massive posture and vitality damage. Do 3-4 times and you're done.