Yeah, like AJ said, the one in the chapel, the Bloody Crow of Cainhurst or whatever, is probably the worst one. The thing is, if you lure him to the steps, get him to use the Chikage's self-health drain buff, and then walk out the door and wait, he'll slowly walk back to his original spot, all while draining his own blood, 'till he dies over the course of like four minutes.