Even within the context of other Soulsborne games, where by the end you're pretty obscenely OP, William is absolutely ridiculous.
Say a normal human fought a single one of the standard Yokai (the big red guys,) it would be a MONUMENTAL challenge. They're fast, hit like a truck if they connect, and won't stop coming after you until they're dead. William mops the floor with a village full of these things by the FIRST LEVEL.
By the time the end of Way of the Strong is done, he can carve his way through enough demons single-handedly that it would make a Dynasty Warriors character blush. He's a storm of blood and sliced limbs, and that's only with a standard katana!
Besides his skill with a blade, he also has mastery over four other weapon types (with more on the way,) command over every element and then some, an almost limitless supply of ninja tools and pills that increase his already godlike capabilities, and if the going gets REALLY rough for whatever reason, the guy has 23 different Bankais, each at least reasonably powerful and a few capable of destroying even the nastiest Yokai in SECONDS.
And he's fast enough to dodge bullets.
I really appreciate Koei putting in the transformation aspect too, since it leads me to believe Japan in-game is full of badasses with magic ghosts, AND YOU CAN PLAY AS ALL OF THEM.
(Except the female ones, for some reason. Playable Okatsu when? I'd even take the male voice clips!)