Yeah, The Last Airbender sucks.
The show's awesome, but the movie's absolutely terrible.
I don't even know why the movie was ever made in the first place, I mean making a movie off the show was already a pretty bad idea. (Unless it's done right, of course, but most show to movie or game to movie adaptations suck when it comes to movies).
Anyway, for my worst movie (or movies), I'd have to say Food Fight, Twilight, Frozen, and Titanic.
Titanic, because it was just way too over dramatic/or at least overdone and cheesy, Frozen because the songs were annoying, and the movie honestly didn't even make that much sense, and Twilight and Food Fight go without explaining.