Who is the strongest enemy in Bloodborne?

I'm curious to know, in the realm of Bloodborne, which adversary stands as the ultimate challenge, the one that strikes fear into the hearts of even the bravest hunters? Is it the twisted abomination that lurks in the shadows of the old hunters' dream, or perhaps the grotesque monstrosity that guards the forbidden secrets of the Yharnam Underground? As a seasoned player, I'm eager to hear your thoughts on who truly reigns supreme as the strongest enemy in this dark and twisted universe.