Since Poseidon is a god from Ancient Greek, there are no records or stories of what Poseidon fears, and most people do not believe in Greek gods anymore. However, since he is immortal, my guess would be being tortured and placed in Tartarus.
A soul
jelly fish are his biggest fear because when he was making those creatures one of them stug him he was really scared
nothing
kronos
no
Poseidon does not fear Zeus, he respects his older brother because he is the king of the gods in Greek Mythology (Zeus is Jupiter, Poseidon is Uranus in Roman mythology).
Zeus and poseidon
Poseidon feared nothing.
a war of the gods
Quite possibly, as Cronus the father of Poseidon swallowed him shortly after birth.
a war of the gods
Poseidon was afraid of this brother Zeus. (actually, he was afraid of the sky, because Zeus ruled it.. )
Poseidon ruled in the sea which surrounds the entire city of Greece and he was considered the god of the seas
Poseidon fears nothing gives nothing and needs nothing
Sailors feared Poseidon, because they believed him to be the cause of earthquakes.
Poseidon's Greek name was Poseidon. Poseidon's Roman name was Neptune.
he is poseidon