I'll start off by saying that I've watched a lot of bad movies. I've seen the non-MST3K version of Eeeegah!, and Troll and Troll 2, before it was cool, and became a 'thing'. Also, what people consider 'bad' is pretty open to interpretation. Right off the bat MagnumPEI struck a nerve with Napoleon and Pilgrim, and Jaws has even made an appearance.
I'll stick with the most disappointing movies for me. Or things that managed to ruin future franchises with their stupidity. Here we go :
Indiana Jones and The Kingdom of the Crystal Skull
Indiana Jones is such an action movie icon, and the first three movies almost a lesson on how to make a popcorn adventure flick. I think that a full movie on how Shia LaBouf befriended and became King of a South American monkey collective and trained them into an elite fighting force, would have been a more engaging movie.
Sucker Punch
Coming off of 300, Zach Snyder was coming off of a high, with a new visual style and comic book feel to his delivery. This movie should have been an indication to everybody (including executives) that he is ALL visual style, and doesn't know how to tell a story. And then they gave him Man of Steel. Sucker Punch is here because it was a gateway to the possible destruction of the DC Universe.
Star : Trek into Darkness
After watching this movie, you will realize three things. 1) There is no longer a need for spaceships. 2) Everybody is immortal now. 3) Spock is the most emotional cat in Starfleet. These arn't even spoilers. Seriously.
Daredevil
My favorite comic growing up. No one making this movie had any idea what to do with the source material. It took the Spiderman 3 villain overload and plunked them into an origin story, that was Batman's origin story.
Avatar
I've touched on the ridiculousness of Avatar a couple of times. It doesn't stand up to repeated viewing, and we are going to have to listen to the sequel talk for half a decade now. It's here because of past hype and future hype, and it's all going to be pretentious as hell.