What series/book/story that you liked in the beginning disappointed you the most?

[Serpentine]

(skippin' right over whatever arguments are going on now)

Heckin The Ill-Made Mute, The Bitterbynde trilogy, by Cecilia Dart-Thornton.
It started out really interestingly. At the beginning, the main character had no voice, no gender, a horribly disfigured face, and no history, and was incredibly interesting, in this intriguing world that was a mix of fairy tales from our world and brand new concepts.
At the end of the first book

Spoiler

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the main character could speak again - and did so in "thees and thous", was a woman, was incredibly beautiful, had all her memories restored, was in love with the incredibly handsome fairy prince, and was deeply, profoundly, boring.

It was so disappointing that all these components that I liked when I was reading it, like the references to IRL fairy tales, started feeling like lazy writing instead.