The X 1999 movie is pretty sad considering what it could have been. X is one of Clamp's masterpieces, and the tv series is pretty good, but the movie is so rushed that it is almost incoherent. Characters who should have major storylines are killed off in the first few seconds of the movie. Its only memorable for the lengthy shots of heads being chopped off and sailing through the air. If you think Dragon Ball Z is nonstop fighting then wait until you see X.
There is something worse though, Gilgamesh. Unlike the X movie that dumbed down the story into nothing more than slick combat. Gilgamesh wanted to be deep. It had all of these undeveloped plotlines that it could not weave together well from a generic dystopian future to some thin references to legends from ancient Sumer, to a gothic mansion, two emo teens, cloning experiments, debt collectors, demons dropping out of the sky, long lost relatives popping out of nowhere-- it is all over the place. Has the worst pacing I have seen, villains who wonder in and out of the story without clear motives. The X movie was shallow and rushed, but as per usual it had Clamp's sleek shoujo art. Gilgamesh is a messy trainwreck of 23 episodes, it has no redeeming features.
Miyuki-chan in Wonderland is my pick for #1 worst anime. I love Alice in Wonderland and reading and viewing its many retellings. This has none of the imagination or world-building I associate with Clamp, it is not a genuine effort to transport us to a magical world, Its just poorly written ecchi. It fails miserably at any attempts at humor, Miyuki-chan is simply an excuse to show panties. Short as it was this mindless movie was still a complete waste of half an hour... at least Gilgamesh tried, Miyuki-Chan in Wonderland is plain lazy.