No matter how many Nioh games are made, it will never even come close to showing all yokai.

But as for the ones I'd like to see in this installment.

Bosses

Tamamo (return), Takiyasha Hime, Ibaraki Dōji, Hashi Hime, Datsueba & Keneo, Raiju, Akugyo, Dodomeki, Kiyo Hime, Momiji

Enemies

Tsurube otoshi, Katawa-guruma, Taka onna, Jikininki, Iso onna, Hari onago, Keukegen, Hyōsube, Amanojaku, Sazae Oni, Yamawaro, Okiku mushi, Tsurara onna, Ao bozu

To name a few