1. DC's Stargirl
DC's Stargirl may not have taken place on Earth-Prime, but it too was a significant part of the Arrowverse's multiversal umbrella, so it wouldn't have felt right to exclude it here - especially as it was also affected by the cancellations that marked the beginning of the end for this DC TV shared universe.
The most jaw-dropping thing about the series finale of DC's Stargirl is that it wasn't altered by the unexpected cancellation. Yes, according to showrunner Geoff Johns, one scene was changed, but overall, the finale remained unaffected by The CW's decision to prematurely end the show. And that's what you call damn good planning.
The Stargirl series finale is a work of art; the perfect culmination of a 13-episode arc that slowly played out leading up to this episode, twisting and turning before it reached its final destination in the Blue Valley junkyard. That finale battle is an overstimulating, over-the-top, and expertly choreographed showdown that highlighted the very best of this show, showcasing that stunning actiony, ambitious stunts, and insanely high production values.
This show had a knack for treating each of its seasons like 13-part movies, so the fact that it wrapped all of season 3's storylines up before the credits rolled shouldn't come as a surprise. What may come as a surprise is how well they pulled it off, while also giving us a glimpse of the future that featured incredibly satisfying fates for all of our favorite characters.
Stargirl's series finale left us wanting more, but it also left us feeling fulfilled and satisfied. You can't really ask for more than that.