There are a lot of them in prequels and sequels, so those get the first section:
A sequel to a story that was clearly finished. At the end of Jaws, the shark is dead, damnit. There is no longer a killer shark, that was the point of the movie. Aliens was fine; the heroine had been left in a vulnerable situation and there were a lot of unanswered questions and a definite possibility of something related happening again; At the end of Alien3, Ripley killed herself in the process of bringing down an alien queen. In a way that left no chance of survival and no recoverable DNA. There was nothing to resurrect for another film. There is only the possibility of a sequel if you have living characters, there are more adventures/horrors to be had, or at the very least there is a distinct possibility of something from the original film carrying on through a whole additional film.
A sequel that makes the previous story pointless. Back to the Alien films, because they give examples of most things that can go right and everything that can go wrong with a sequel. The second film ends with the heroine getting out with the little girl that she's been desperately defending the entire film, the emotional core of the story, Ripley's reason for fighting. But they won. They're safe, and they're going home. There's still a massive evil conspiracy and a species of incredibly dangerous monsters that she's probably going to have to deal with, but that is a matter for the next film to resolve! And then Alien3 comes along and murders the girl, without a word, in the first minute, offscreen. And dumps Ripley somewhere that she can't do anything about the overarching conspiracy-and-alien-race plot she's been gradually figuring out. What was the point?
Prequels that insist on using every single character from the "later" films. The new star wars films, for example. We know that Anakin will be trained as a Jedi, betray them, and become Darth Vader; there's no way around that, and we're here to see the how. And Obi-Wan and Yoda are almost certainly going to need to be a part of this story. Also, we're going to see the fall of the Republic and rise of the Empire. But why the **** are the droids here? The droids that play major roles in later events and have no knowledge of the history that we're about to see? There have been, contrary to some earlier posters, good prequels. In Tolkein's The Hobbit, we know that Bilbo, Gandalf, and Gollum will survive, and that Bilbo will acquire the Ring and take it to the Shire. Everything else is left open, and there's actual tension and mystery because most of the characters aren't immortal and most of the events are unknown. But then some idiot decides that they need to port everything from the original film into the prequel, despite the fact that it's been established that none of these people know each other and none of these inventions exist until later in the story.
Post-production 3D. 3D is not a very good idea to start with, because if it works you don't notice and if it doesn't work it ruins everything, but it doesn't have to suck. If you film in 2D and then edit it into a bunch of cardboard cutouts, it'll suck.
Shaky cam. It's designed to look realistic or make you feel like you're in the scene or whatever, but they clearly do not understand how the eyes of brain work. A real person running automatically stabilizes the image in their brain, so it's not quite as precise as standing and looking carefully but you can tell what's going on. A camera does not, and the viewer can't adjust because their head isn't actually moving, so all you're doing is making it impossible to see and inducing nausea in anyone attempting to watch as their brain tries to deal with mismatching signals.
Changing camera angles constantly in action scenes. If I'm watching an action scene, I'd like to be able to tell what actions are occurring, thank you very much. Every time you change the camera I need to figure out who's who, where they are, and what they're doing. And then you change it again before I get to the last step. So those multi-million dollar effects and brilliantly choreographed fight scene just turned into a bunch of faceless anonymous people with epilepsy.
Gratuitous nudity, gore, etc. I have no problems with adult content if it matches the themes of the film, fits in the story, etc. If it was blatantly tacked on to increase the rating or draw perverts, it becomes disgusting.
Stupid anachronisms. I don't have a problem with schitzo tech that fits the setting, or using modern american english in a historical/futuristic/foreign setting in order to allow viewers to understand what's going on. But if you're in a standard medieval setting and at the fancy ball you throw in a rapper and everyone starts freak dancing, you've just killed the movie.
Bullshit scientific explanations. I'm perfectly fine with a handwave on how the time machine or the hyperdrive works. I will accept a barrage of terms that sound scientific to people who don't know science. I will not accept an explanation that takes real scientific principles and terms and pretends they work in a way that has nothing to do with how they actually act. For example, the "black hole = time travel" trope that has become so common. Yes, it's been theorized that you can effectively travel forward in time by moving at speeds approaching the speed of light, because your own perception of time would be slowed by relativity. Yes, you can achieve these speeds by looping around a black hole (if you're a suicidal moron). No that does not mean that you can dive into a black hole and come out in the past; no part of that has any grounding in any actual science. Just make a damn time machine macguffin and stop pretending to understand things that you clearly don't.
Any film built entirely around one famous actor. If Jack Black, Eddie Murphy, or Will Ferryl is in something, you know from the start that it's not going to be a movie, it's going to be a shrine built to one person who isn't as funny as they think they are.