Smough and Ornstein. Beat them a few days ago for the first time. Actually wasn't that hard once I summoned solaire and kindled the nearest bonfire for 10 estus flasks. My problem was being patient. I'd keep getting fatty as the last one, and near death, but would get greedy and try to just hack the rest of his health away before he could kill me, he always killed me. Finally took my time and poked him to death.