Namor Legends: Warlord Krang
Warlord Krang first appeared in 1963 as an Atlantean military leader and advisor of Namor, scheming against his king to overthrow him and allying himself with characters like Attuma, Byrrah, and Lemuel Dorcas to accomplish his schemes. Basically, the evil advisor trope as a fishman.
In an adaptation, I think he might be a good starter villain, especially acting behind the scenes while someone like Attuma and Dorcas are the more central focus, possibly building to the reveal that he was involved the whole time. As for casting, I hate to cast Ben Kingsley in this role, since he plays it a lot and I don't think I ever like him in the role (his more heroic roles are way better), but he does look a lot like the character.
