Do bonus bosses count? Because Darkeater Midir brought my Dark Souls 3 playthrough to a screeching halt because I didn't want to lose the titanite slab and covenant I'd get if I beat him before the penultimate boss of the DLC. I just could not figure him out- He triggered a frustration that his fellow true Dragons Kalameet and Sinh didn't. Kalameet was tough but fair, and Sinh was annoying (too much flying around out of reach), but neither shut me down the way Midir did.