These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Fashion-Victim Villain: Played with when Drizella messes with the Fairy Godmother's wand by changing her clothing. She gives herself giant jewelry, big hair and a giant dress, everything in clashing colors.
Moral Event Horizon: She may or may not have already crossed the MEH by that point (see the YMMV page for the original classic for her earliest possible MEH), but Lady Tremaine definitely cements it in this film when she poofs Cinderella in a twisted pumpkin carriage with Lucifer as its human driver, and attempts to get Lucifer to kill Cinderella.Especially heinous because up until that point she was satisfied with just making Cinderella's life a living hell.
She also has Anastasia posing as Cinderella to fool the prince. If anyone doesn't know, this is rape by association... and for worse, she tries to use one of her own flesh and blood daughters for such shit, and right when Anastasia is becoming more and more sympathetic!
Narm Charm: Lady Tremaine chanting, "Bibbidi, bobbidi, boo!" to kick off the time-reversing spell.
Spoiled by the Format: Prince Charming rescues Cinderella from being sent far away and are on their way to their wedding... only there's twenty minutes left in the movie.
Tastes Like Diabetes: The first three minutes of the movie, in which Cinderella recounts her rags-to-riches life to the viewers before she, Prince Charming, the mice and the Fairy Godmother sing about how "Perfectly Perfect" things have been since the wedding.
Considering the amount of Lampshade Hanging in III, that may have been a deliberate effect to contrast the rest of the movie.