Stupidity: Early in the film, Peter Parker desperately wants to see Mary Jane's performance, but he is turned away at the theatre doors because he is a few minutes late. Defeated, Peter shuffles away and sulks. Seriously? Why couldn't Peter simply enter the theatre through a side door or the roof? He's Spider Man.
Suggested correction: There's two things to consider here. First, a major theme of the film is Peter struggling with keeping his Spider-Man and Peter Parker lives separate. Peter makes every attempt to get to the show on his own, as Peter by riding on his scooter. Simply breaking into the theater after he has been turned away would ruin the idea that keeping his two lives separate is a struggle. It would instead imply the opposite, that Peter can simply use his powers to solve his problems whenever it's convenient. Secondly, the usher makes it clear that no-one is to be admitted after the show has started as this would disturb the guests and possibly the performers as well. Sneaking into the theater could very well ruin the performance and Peter obviously wouldn't want that.
If there's one thing we know about Spider-Man, it's that he is incredibly stealthy, often coming and going without any detection whatsoever. He could have easily accessed the building and watched the show from a secluded vantage and even met Mary Jane backstage afterwards. Certainly in this case, using his powers would be justified, given that it was more important for Mary Jane to know Peter attended the show, rather than simply giving up.
He doesn't want to do any of that, though. He wants to go to the show as Peter, with a ticket, sit in a seat with the rest of the people, enjoy the show, and see Mary Jane afterwards. He stops the car chase as Spider-Man after his scooter is wrecked and instead of web-swinging to the theater, which would have been much faster, he chooses to change back into his regular clothes and drive the criminal's car. Sure, he certainly could have used his powers to get into the theater but the point is he doesn't want to. The fact that he chooses not to use his powers and instead deal with the consequences of hurting Mary Jane's feelings is the entire point.
And besides he'd probably get kicked out of the theater if he was caught.
Stupidity: Marta is shown to barf whenever she lies, and Blanc knows this. He should've asked her who did it right away. The entire plot of this movie is rendered unnecessary.
Suggested correction: That would only work if Blanc knew that Marta had knowledge of who killed Harland and if he came to the conclusion that Harland actually killed himself. Blanc doesn't know that Harland killed himself to protect Marta until Marta confesses. Also, this wouldn't have solved the "who done it" anyway, since Marta had no idea that Ransom switched the vials.
Stupidity: A major effort is put in the future to develop the time portal, so they can recruit people from the past to help fight the war in the future. Yet they never seem to think to share anything with the past about the creatures and how to kill them or find out where they came from so the can help either prevent it from happening or help save the future before humanity is wiped out. Muri does recruit Dan for this purpose but it seems wasted to only use 1 person for this much more important goal.
Stupidity: Lecter fires the first bullet to alert the police that something is up, and the lift goes up, then comes down. Now in all this, only 6 or 7 go up the floor where Lecter was. Why aren't police sent in groups to investigate every floor? Lecter could have been anywhere, instead there are about 30 police huddled on the lobby floor.
Stupidity: It was pure stupidity for Riggs to bring Rika back at her residence after escaping the hit on Riggs. The villains know where Riggs' love interest lives and this nor the option to hide somewhere else or safer never occurs to him?
Stupidity: Hans keeps a major part of his plan secret from his own team: that the electromagnetic lock will be disabled if the FBI shuts down power to the building. The mercenaries hired as muscle don't need to know the minutiae of the plan, but it seems ludicrous that Theo wasn't told. Theo states on more than one occasion that he can't proceed past a certain point and that he hopes Hans has a plan for the final lock. Evidently, Hans was keeping this information secret simply to amuse himself, which makes little sense considering how much planning went into the heist.
Suggested correction: Or because he simply doesn't trust anyone with that kind of knowledge. He neither trusts them or cares about them, it's all him.
So he trusts that Theo would be on board with all the murder and mayhem, open all the other locks, be in a tactical lookout position when the police try to breach, and drive the getaway vehicle. But he doesn't trust Theo enough to tell him the last lock will open when the power goes out?
It's not about trust; Hans needs Theo to do what he is there for and that is all you mention up to the final lock. He has a plan for the final lock and so there's no need to discuss it with the team, since it won't be any of them responsible.
The more people that know the plan the more chances of someone talking. Especially when they are hired mercenaries.
Theo was already on board with taking hostages and committing murder. Him knowing that the power needed to be shut off to open the last lock doesn't appear to be particularly important information you would need to keep from someone to keep them from talking.
If he's the only one that knows the final step to get the money, then at least up until that moment he is absolutely indispensable to the plan and ensures no-one would double-cross him. In any case I'm not sure being more cautious than necessary really qualifies as "stupidity."
Stupidity: Mr, Freeze and Poison Ivy join together and plan to cover Gotham in freezing temperatures and plants, with none of them ever considering in the slightest that plants don't survive freezing temperatures, despite both of them being scientists.
Suggested correction: Poison Ivy made super-plants that could survive the new ice age they were going to create. As for the fate of normal plants, though this is only really clarified in the novelization (and original script), Poison Ivy's god complex has (pun intended) grown to where she no longer cares about individual or existing plants, just playing out her fantasies of being "Mother Nature."
Stupidity: When the parents knew Freddy was doing the killing then why didn't they watch him like a neighborhood watch so they could catch him trying it again, and thus avoid the legal technicality which threw out of the first case? It seems idiotic they broke the law to punish this lawbreaker.
Suggested correction: The parents believed Freddy would not face justice for his crimes. They were unwilling to allow him the opportunity to kill another child, and believing the justice system had failed them they took the law into their own hands. They completely got away with their vigilante justice. The only bad thing that happened was Freddy was brought back as a vengeful demon with superpowers. There is no way the parents could have known this would happen.
It is still a stupidity. Even if they wanted him to suffer, they would try to avoid legal problems at all costs. It is good that they wanted to prevent him from killing another child but they still shouldn't act so hastily.
Stupidity entries are not meant to be stupid acts by characters. They're for minor plot holes. Without in-film evidence why the acts would be a plot hole, there is no stupidity mistake. And assuming what characters would or would not do does not make a valid mistake (not to mention revenge killings do happen in real life and in movies a lot).
No, it's not. What else were they supposed to do when he was caught and set free? It's still not their fault what happened next.
Stupidity: Batman finds the Ice Princess on the edge of the roof, standing on the wall. If she's no longer bound, why didn't she just jump down onto the roof and negate the risk of falling to her death, which she did?
Stupidity: In the scene with the water-jug puzzle, both Zeus Carver and John McClane initially suspect that the small carrying case contains a bomb. McClane goes ahead and opens the case, which confirms that it is a bomb (the electronic readout in the case even says: "I AM A BOMB. YOU HAVE JUST ARMED ME"). If they suspected it was a bomb in the first place, why didn't Carver and McClane immediately try to warn the dozens of pedestrians all around them to evacuate the area before McClane opened it? That would be a seasoned police officer's first instinct. Instead, McClane and Carver banter and bicker and never attempt to warn the public, even as the timer is ticking down.
Suggested correction: This carries over from the very first time McClane and Zeus talk to Simon on the phone (the "As I was going to St. Ives" scene). Simon tells the two not to run and McClane assures him they won't but that there are at least 100 people on the street, to which Simon responds "That's the point." McClane takes this to mean he can't just warn everyone or Simon will set the bomb off. They open the case because they don't know that doing so will arm the bomb. They wanted to know if there was a riddle or more instructions. Having the bomb be armed by being opened, complete with the pithy text "you have just armed me" was just a way for Simon to torment McClane. The bantering and bickering is of course, still pretty stupid but is consistent with how the characters behave for the entire movie.
Still, McClane's whole motivation in this movie is to save innocent people from death, which goes above and beyond his motivation in the first movie (which was to save his wife). What is the whole point of disarming the briefcase-bomb in the park if not to save the public? As stated in the original post, no seasoned and dedicated officer of the law would proceed without warning the public.
Except he was told specifically earlier not to do that. If he warned people of the bomb, it was implied that Simon would remotely detonate it. It can't be "stupid" of McClane to not warn people if he thinks doing so will get them killed. I agree that it is a trite movie cliche that a cop doesn't act like a cop would in the real world, but in the context of this film McClane's actions are consistent with the instructions Simon gives him.
Stupidity: When the teens are about dump Ben Willis off the pier, he regains consciousness and snatches Helen's crown. Despite knowing he's alive with strength to spare, they nonetheless drop him in the water and continually refer to him as "dead."
Stupidity: Oldboy finds the right Blue Dragon restaurant that the prison uses. But him running after the delivery boy doesn't make sense. How does he know the delivery boy is going to the prison? He knows it's the right takeaway, but that's all he knows. So, would he have a moped, bicycle, or car ready to use surely? The takeaway is a long way from the prison (as he says himself in narration), so he wouldn't just wait around for a moped delivery to run after, especially as a good chance he wouldn't be able to keep up.
Stupidity: While Tommy and Snake Eyes are trying to escape the docks in the truck, the Yakuza men surround the truck and stab over a dozen swords in all parts of the cab. Not one of the men ever thinks to use their sword to slash the tires, allowing the heroes to make an easy escape.
Stupidity: Adam, Hannah, and Megan [sitting in SUV with flat tire] saw the Man flashing his headlights, getting out, kicking his own SUV and ranting while holding a machete. Instead of fleeing, they got out of their SUV and saw the Man was wearing a welder's mask. When they returned to their SUV, they didn't lock the doors. The Man ran over, pounded on the front passenger's window and then opened the door. He stabbed Adam 36? times while the two girls just sat there screaming and one said, "Please stop."
Stupidity: Since the main people could not delete, or even change their own Facebook accounts; why not contact Facebook support in order for the company to do it for them?
Stupidity: When Bishop is first holding the gun on Gina in the cabin, he stands close enough for her to grab the gun and try to get it off him. A man of his experience would never make that mistake, it's one of the basic rules of controlling someone at gun point: Stand more than an arm's length away.
Stupidity: In 300 years, in an empoverished world full of people hungry for techs, nobody ever tried to remove the ship from a small pond barely 15 feet deep, and everything inside seems intact. It is mentioned that few tried because the technology is hard to sell being unknown (which is laughable), but surely some would try to strip the ship for alloys, and certainly the lights and monitors wouldn't stay untouched in a world based on scavenging. For 300 years and so close to the city, even.
Stupidity: When the army base gets overrun the girl jumps on a soldier and starts biting his neck. The woman soldier that's with him aims her gun at them but doesn't shoot, knowing full well there's no hope for the man. There is utter carnage going on all around them and instead she tries to help him and gets attacked in the same way. This could be a plot hole as well as the girl in question is the one that holds the key to survival.