Bloodborne Undead Giant (Cheese)Cursed/rotted/fetid Pthumeru Ihyll Layer 2 depth 5

OMFG, hate this boss. Literally wasted 2 hrs of my life to beat it in the much harder cursed/rotted/fetid Pthumeru Ihyll dungeon. Almost every single one of his damn attacks would 1 shot me even with 740 hp (all hp% runes). Tried all methods and weapons and found he has different attack patterns hitting anywhere from 2-5x in a row. I eventually gave up completely on fighting him from behind and tried a new safer method that would prevent any mess ups dodging behind him. This method would allow him to complete his entire atk animations, then sprint r1(reg. atk) him, retreat and repeat. I found doing this worked quite well because he would be too slow to recuperate before you get out safely. For whatever reasons, I found that switching back to my blade of mercys and strictly only moving diagonally the entire fight, he only did 2 swinging motions that would leave an opening every single time.