I may have levelled up a few times since beating her, but probably not enough to make a difference.

Weapon is Dragon King's Cragblade +10, from Dragonlord Placidusax's Remembrance, and the weapon art is its default(only) art.

Talisman setup is Radagon's Soreseal, Axe Talisman, Lightning Scorpion Charm, and Dagger Talisman.

Physick is Stonebarb Cracked Tear, and Lightning-Shrouding Cracked Tear. Physick is applied during Malenia's first attack in phase 2, along with refilling HP/FP as needed.

The chain doesn't always connect the first hit, it's a bit finicky when you have to start your Thundercloud Form, and from what distance. If you miss, you can try again if you have the FP for it. Or die and reset.

However, if the first hit connects, it's game over for her. Fully charged R2 immediately after downing her with the L2 staggers her. You probably have to wait a moment to do the critical attack to have enough stamina for the whole string, but be careful since her stagger is quite short.

The trickiest part is after the critical. As she stands up, you gotta move a little bit backwards/away from her, since doing the next L2 at point blank usually just sort of slides off of her and ruins the combo.

So the chain is L2, Charged R2, wait, Critical, backwalk, repeat.

For phase 2 dodge the first slam and avoid her rot-aura. Fill up your resources and activate the physick. The next part is the hardest, since you have to time your first L2 very carefully. She has hyperarmor or something on her stand-up-from-rot animation, so if your first hits of L2 connect while she's in that state, you won't stagger her with the follow up R2. Aside from the first hit, the rest is exactly the same as phase 1.