I've beaten the Souls games and Blood borne, a bunch of Final Fantasy super bosses, Raam on the highest difficulty, etc
But this motherfukker is the only one who straight up made me restart a game
(I know that pick doesn't actually show the fight, but it's an appropriate introduction)
I got that game the day it came out, so nobody knew about yell/accumulate trick, poaching your own monsters for crazy gear, etc. I only had one slot left on my memory card and this nikka just eviscerated me at least 50 times
Had to start over from the beginning, was so pissed I didn't even touch the game for a year.
Always go ninja and yell/accumulate til I can 1 shot this dude and all his goons when I replay it now