Spiderman 3 - I was so excited when I first saw the trailer, then when I finally saw the movie I was so let down. I can look past the crappy dialogue, strange sequences (emo peter?!) and the fact that every major character at some point in the movie was crying their eyes out. I can even overlook the plot holes.....
.....but the fact that Sam Raimi took my favorite character Venom, made him out to look like some scrawny little runt, and gave him less than 30 minutes of screentime is absolutley, positively unforgivable.
"You drank a charm to kill John Proctor's wife! You drank a charm to kill Goody Proctor!" - Betty Parris to Abigail Williams in Arthur Miller's The Crucible