This study examines the evolution of gender power differences within the Omegaverse trope on the Archive of Our Own (AO3) fanfiction platform. The Omegaverse, a fan created trope defined by distinct secondary gender categories (Alpha, Beta, Omega), provides a lens to explore and critique gender dynamics. We used connotation frames and the Riveter NLP pipeline to measure power dynamics in Omegaverse slash relationships between characters. Our corpus includes English stories across eight prominent fandoms, including Japanese anime, K-pop, Western TV series, and Western films. Our findings show Alphas generally exhibit higher power scores than Omegas, consistent with the trope's constructs, but with notable variance between fandoms, while most fandoms exhibit more within-group consensus when more fans start writing. This research offers insights into how fan communities evolve and challenge traditional power structures.