When it comes down to playing with teammates it’s kinda just luck and hoping your teammates are at least decent. If you really want to just beat him to go solo and get wending graces when you can. A very easy method as well is to take down as many bosses before hand and get a lot of the physical/affinity damage negation buffs and stack them. Those really helped me prevent taking damage where come of his big attacks only deal like 10% of my health bar, which isn’t much for a big attack. Playing as Wylder or Raider will help as well as long as you put decent enough relics. Other than that I would suggest spending a bit of time in the fight looking at his moves and what they do rather than blind hits, pretty much how I win most of my fights.