4. The Borg Queen
Part of the threat of the Borg as initially conceived was that they were a threat individually and as a whole. There was no "head" to cut off to stop them; the threat was spread throughout the entire collective. Stop one Borg and forty more would take its place with the same knowledge instilled in it. More so, whereas previously in the series the assimilation process seemed to be a lengthy process, it was now almost instantaneous. More Borg were just a pinprick away. Writing wise for a movie, the introduction of the Borg Queen was almost a necessitythere needed to be a definitive villain to beat instead of an entire collective as a whole. While I thought it was beautifully acted by Alice Krige and handled deftly - especially the subplot with Data being potentially turned by the Queen with the promise of becoming more human - overall it diminished what the Borg was for future endeavors, and made them just a little less unique in the Star Trek mythology.