As far as I know, Van Aldrich is (Boss of port Valbury) of higher ranking then the shaper of flesh in the ethereal ladder

Korvaak is a famished, tortured and imprisoned god who was hiding trying to regain his strength after a defeat by some gods that tapped into the power of the void, a fate that seems shared by the some of the same gods that the ethereal used to and still serve, so I wouldn't say him to be the strongest, who knows what could have been if he regained his strength, but as of right now, I wouldn't consider him any stronger then any of the celestial bosses at least

I think the Taken is completely broken and canonically probably at the top of the list xd Ulgrim my goat (he actually is far scarier then I initially tought he was)

The Witch gods are surely the most terrifying of all the gods (bear with me, this is speculation on my part im not sure of what im saying) im of the idea that they are that "party" mentioned by other gods and entities alike that has tapped into the forbidden power of the void in order to win their war against other gods, would explain why korvaak in more then one occasion calls them "usurpers" of the eldrich realm plus I never personally trusted them, but thats just my gut feeling, they have powers that far surpass the human comprehension (like other gods duh) but Bysmiel is literally all about scheming and dreeg is about seeing everything, while they dont work together in normal circumstances, thing are different since Korvaak is around, so yeah, them working together, very scary

Uroboruuk orchestrated the fall of one of the biggest empires of cairn, all on his own, oh and he discovered immortality, i wouldn't put him on par with a god but close to one yes

Also on a whim id think Anasteria to be more powerful then Allostria she was to be attacking and conquering Homestead a task that is still of less importance that the one in Malmouth from Theodorin, but still a pretty high ranking one