the great thing about the final confrontation between Poseidon and Odysseus is that this saga wasnt about someone seeking Vengeance. It's about the concept of Vengeance itself. About the cycle it traps us in.
Odysseus and Poseidon both were trapped in the Storm. A Whirlwind Prison of Poseidon's own making that neither could escape from now. How fitting, because thats all Poseidon knows. The Prison of Revenge. Of Blood for Blood.
Odysseus wasn't stabbing him to seek vengeance. He was crying out to Poseidon. Begging him to relent. To Forgive. He just had to speak it in the only language Poseidon understood.