Here's my little list.
Transformers: Revenge Of The Fallen Far too much humour, all "darkness" promised by Bay completely absent because of over the top/amount of humour, retarded/illiterate twin robots, robot dieties, religious epithany of robot dieties, Optimus sailor mooned back to life, no feeling of "good guy" characters are in real danger, terrible portrayal of war even by sci-fi standards. awful writer (ehren kruger).
The Last Airbender Bad acting, bad story/plot, bad dialogue, bad choice of actors, M. Night Shamalan as writer/producer/director a very bad combination.
G.I. Joe: The Rise Of Cobra Bad acting, bad dialogue, bad actors, bad story/plot, bad writers, no sense of realism, awful visual effects, bad choice of actors.