They fought against their father, Kronos (Chronos) as well as the rest of the Titans.
They fought against The Greeks and they lost
He has fought Scylla, cyclopes, minotaurs, centaurs, evil gods, titans, dracaenae, Hyperion giants, and many others.
All of the Olympians participated in the fight, along with the Moirae and Heracles.
The giants were called Titans.
He was a Titan who fought against the Greek gods, so he was punished by being forced to hold the sky for eternity.
Poseidon fought along with the other gods in the war against the Titans. In Percy Jackson and the Final Olympian, he was essential in defeating Typhon. He also fought Oceanus.
The Greeks, led by Agamemnon, who had made an agreement between the greek states. They were aided by some of the gods.
The Ragnarok has not happened yet however it is supposed to be a battle between the forces of Einheriar and frost giants.
I wonder if you aren't confusing "giant" with "Titan". However, there was a less known battle between the Olympians and the Gigantes, giant children of Gaia. This war was known as the Gigantomachy, and the gods nearly lost, were it not for the timely intervention of Heracles. The giants were led by Alcyoneus and Porphyrion.
In Norse mythology, Thor was the god of thunder and lightning, as well as strength and protection. He was a powerful deity who fought against evil forces, particularly the giants, and was also associated with agriculture and fertility. Thor's main purpose was to maintain order and protect both the gods and humans from harm.
Norse mythology is quite complicated, but the main enemies of the Norse gods were the Frost Giants. There is also one Norse god named Loki who was working against the interests of the other gods; probably he was the single greatest threat.