Perseus views Zeus as his real father, and doesn't hold a grudge against Hades.
Io died giving birth to Perseus' son, Helios.
Bubo, the mechanical own, shows up again.
Hephaesthus has a brief role, directing Perseus to the labyrith where he fights the Minotaur.
Ares is the main villain, and is motivated by jealousy towards Perseus, whom Zeus loves more despite Perseus being only half-God.
Zeus and all the other Gods die, aside from Hades, who forgives his brother and helps him defeat the Titans before losing his powers.
The movie ends with Andromeda and her army fighting the Makhai with Perseus defeats Kronos with a weapon that holds the combined powers of Zeus' lightning bolt, Poseidon's water trident, and Hades' dark pitchfork.