Dramas that would be a Perfect 10 if not for the ending

 ArniA:

King Eternal Monarch: Ok I overall liked the series and the end was OK, but I somehow felt betrayed because I had this expectations she would become queen... that's what the ML chanted about the "future queen" and stirred up emotions and stuff,  but that was never delivered, just some parallel reality stuff. I guess they don't know their audience.

This was a drama that had such a great premise that was just ruined with lazy writing. I would love for another country to redo this and redo it well this time.