Isshiki. Jigen would be here too.
Momoshiki. Any form of him that we know of goes here.
Kaguya. Any Post-IT form of her goes here.
Hagoromo. Any form of him goes here.
Isshiki and Momoshiki are the only ones that can be compared via feats; Kaguya fights completely different versions of characters so her scalings just don't work [Kaguya > Teen Naruto < Adult Naruto ~ Fused Momo helps for nothing].
The Kaguya who feared Momoshiki was Prime Kaguya, as she could already create WZs, which means she had already used IT and had the Chakra of the entire world.
The Hagoromo who keeps admitting inferiority to Kaguya is Ghost Hagoromo who has all the indications to have conserved his power when he was Juubi's Jin and nothing implies for that not to be the case. SPSM pattern on his back, has Yin-Yang release (The seal, which he only had alongside Hamura before), multiple TSOs. He just is Prime Hagoromo.
Kaguya Otsutsuki
Isshiki Otsutsuki
Momoshiki Otsutsuki (Final Form)
Hagoromo Otsutsuki (10 tails Jinchuuriki)
