The key if you are sword based is to dash forward to dodge his attacks. Most of his moves can be completely avoided if you get behind him. His thrust attack specifically is an opening to get in a quick quick, quick, strong kick. The ki depleting kick is key to beating him. Stay close and focus on getting behind him to drop his ki fast and use grapples.
Dont give him time to cast spells. His combo weaknesses are close range especially in the 2nd half of the fight where he uses his red aura moves. Most of this red aura moves require you to be close to him which was my first hint. He also spams at long range so all signs point to stay close, dodfe behind him and deplete his ki. It may seem impossible but if you dont get blinded by the flashy moves he is difficult but not impossible to beat. Took me about 15 tries.

my first time fighting this guy when i didnt invest in any magic. i used a mujina soul core for the copy buffs. i got all his buffs and handed him his a**

the funny thing abt human bosses in this game is they need to be given overly powerful spammable moves cuz they will be way too easy otherwise. devs dont have any other way to make them challenging.