Subjugation of the Nine Realms

"Odin and I drowned entire civilizations in blood and tears. Where do you think all this gold came from? And then, one day he decided to become a benevolent king. To foster peace, to protect life. To have you!"

- Hela to Thor Subjugation of the Nine Realms was a conflict between Asgard against the eight remaining realms. After King Bor died in another war, Odin took over the throne and had his first daughter Hela, whom he named his executor and began a series of violent campaigns to conquer all the remaining realms, the result was that Asgard managed to prevail in front of the other realms and initiated the hegemony of Asgard as the center of the Nine Realms. The war ended after Thor, the second son of Odin and Frigga was born; for Odin wanted to become a benevolent and peaceful king.

History
The oldest child of Odin Borson, Hela served as her father's executioner and the leader of the Einherjar, helping him conquer the Nine Realms. Odin, however, after realizing that bringing peace was the true way to unite the Nine Realms, saw Hela's over-ambitiousness, combined with her formidable powers, as a threat and ultimately Hela became too ambitious and attempted to take over the throne sometime after Odin became a peace-time king. According to Valkyrie, Hela massacred many Asgardians in the Palace and attacked Odin, who finally was forced to accept that Hela had grown too dangerous and battle her in the process. After defeating Hela but also showing that he was incapable of killing her, Odin banished her from Asgard by imprisoning his only daughter in Hel for millennia with his life force acting as the lock to her prison.

Odin then proceeded to write her out of Asgard's history, even going so far as to replace the mural depicting her conquests in the throne room of his palace with images of his new children.