Even though it's my absolute favorite FF, I would have to say X-death. He's a very basic, pan-and-paper villian. He goes "Mwa ha ha!" alot. Very cliche, and very annoying. The translators could've done better.

Say what you want about Sephiroth, Ultimecia or Seymour, but X-Death is my personal definition of Lame Villian.

This post would be incomplete if I didn't mention Kefka being WAY over the top. Square tried too hard to make the player hate him, I think.