This reminds me of Galadriel: "In the place of a Dark Lord you would have a Queen! Not dark but beautiful and terrible as the Morn! Treacherous as the Seas! Stronger than the foundations of the Earth! All shall love me and despair!"
Even through I was partial hoping for more of a transformation but then the redemption of Trixie and reasonable enough for Twilight and her friends to defeat Trixie in a believable way. However the end we got was a little too cheesy for me but I should complain that the ending was more a slice of life ending but it is meant for kids so be thankful what you get.
Do like the villainous look that Trixie has a Chrysalis/ Celestia look which is really astonishing and a nice contrast. Reminds me of how King Sombra meet his end.
But if I had an ending in mind mmmmm I would have had a transformation and Trixie defeats everyone the Twilight Sparkle talks to Trixie appealing to her inner good and talks about friendship. Trixie replies somebody of her caliber doesn't need friends. Which then either Twilight or one friends catch on that she is lonely and comments or asks you have no friends. Do you? In which she acts out in rage against that individual replying that friends only bring you down (if time flashback to Trixie's supposed friends ie bullying her and maybe if lucky explains her dislike of wheels). The the each go around briefly explaining why friends make you better ending with Twilight. Who says she'll be Trixie's friend. Then coaxs Trixie to remove the amulet herself. Then Trixie replys angrily YOU TRICKED ME, YOUR NO DIFFERENT! In which Twilight replies No I was helping you. You weren't yourself, friendship can be painful at times but the results are something else. -->You get multiple lessons Nobody is a lost cause, Not everyone is the same and people can change. However I feel this is going to be the theme in the Discord and Fluttershy episode.
Along those lines sorry for posting on your lovely image it just inspired me.