The Dancer of The Boreal Valley from DS3 will always hold a special place in my heart, more for the fight itself.
The Dancer's lore is tragic, but relatively brief. She, once a maiden of Gwynevere, was turned by the Pontiff into a relatively mindless monster and defender, although it can be argued that she may have preserved a bit of herself through the greater context of her presence within the game.
However, as stated, the fight against her is even dearer to me. It really does feel like a tantalising dance of sorts, with both partners forcefully alternating the lead, lunging and retreating over and over again, like two forlorn lovers. She is beautifully animated, so much so that I've let her kill me plenty of times just so I could focus on admiring her moveset, her fluidity, her forcefulness. You can feel you're up against a being of immense strength but also blessed with radiant gracefulness. And the backing track is perfect!
The fight against The Dancer is up there with the Cyberdemon waltz from DOOM* 2016 for me in terms of "knowing someone through combat," it's just artfully expressive if you have the patience to allow it to unfold and evolve.