The First Boss: Pieta Fight
Created a crusader just to have a comparison and your starting class matters definitely. I didn’t level the crusader at all and I’ve beaten her second attempt.
Take your two-hander two-handed and try to hit her with a fully charged heavy attack. If you hit, you’ll cancel her attack and “stagger” her for a moment.
Wait about 1-2 seconds to regenerate some stamina, then follow up with the next heavy attack. If you get the timing right, you can stun-lock her until she starts the second phase.
Second phase was a bit more tricky for me, but here what worked in the end for me.
She flew to the other end of the room to summon the two other “angels”, I ran past her (i.e. behind) and started to whack her.
The adds attacked towards the center and she herself only fumbled around, waiting for the adds to finish, so I could just knocking her down, again heavy attack after heavy attack.
While I wouldn’t consider her unbeatable, it’s a rather movement/wide swings intensive fight, including adds, something I didn’t expect for the very first boss in this game (or a game like this in general).
And I think that’s what’s throwing off most people. You’d typically a bulky, not too fast, heavy swings fight. Not a – if I may use an Elden Ring analogy – a buffed up Crucible Knight.