Brief History
The Inhuman, Maximus, was able to harness all of the secret guilt of the Inhumans over the enslavement of the Alpha Primitives. Creating Omega with this power, he used Omega to lead an assault on the Inhumans.
When the Inhumans realized that their own guilt was the source of Omega’s strength, they dealt with their feelings of prejudice, and Omega lost his power. As a result Black Bolt (the leader of the Inhumans) enacted reforms so that all Inhumans would be treated equal.