
Stupidity: Lao Che's intention was to kill Indy. He had no intention of giving him the antidote. So then why would he bring a real antidote? Why not just fill it with something else instead? From his perspective, bringing a real antidote was a waste of time, and also very stupid in case Indy managed to get it, which he did. In fact, Lao Che could've brought a fake antidote and given it to Indy. He probably wouldn't have noticed the difference, and then there wouldn't have been a fight in which one of his men was killed.
Suggested correction: If you're using a poison it is always worth having an antidote nearby just in case something goes wrong.
Lao Che could still have the real antidote in his pocket and give a vial a fake antidote to Indy. Plus, if you're implying Lao Che would need the antidote should he accidentally be poisoned, it would also be a stupidity for him to give the antidote to Indy.
Lao Che's goal is not to kill Indy, it is to get the emperor's remains without having to give up the diamond. He even tries paying for the emperor outright with valuable coins. He brings the antidote in case he loses track of the poisoned glass and the wrong person is poisoned. He never intends to actually give the antidote to Indy, he's only using it as leverage so Indy will hand over the diamond without making a scene. Indy only gets the antidote after he kills Lao's henchman and the antidote is knocked off the table.

Stupidity: After the team break Solomon Lane out of custody, they drive around Paris with him in the front seat of their car. Lane is still wearing a straightjacket, bound in chains and has a black bag over his head. The IMF team drive him through crowded streets, past multiple police cars in full view of everyone just minutes after an armoured convoy transporting a dangerous prisoner (who everyone is now looking for) has been attacked. None of the Parisian police seem to notice this and none of the IMF team questions the tactical soundness of this approach.
Suggested correction: What's stupid about this approach? The IMF team is trusting that with their skills and experience they can easily evade any police that spot them. Which of course they do. Placing Lane in the trunk would have kept him out of sight but that doesn't really matter because they weren't planning on sneaking him out, they were planning on a quick escape.

Stupidity: It's stated that Imhotep will fear cats until he has fully regenerated and two different scenes show him fleeing in terror at the sight of a cat. Despite this, none of the characters that Imhotep is trying to kill that are fully aware of his weakness even think to have a cat with them at all times.

Stupidity: Beck wants to kill Peter's friends because they know his secret. Instead of using Edith to attack them directly with a drone strike, or using his illusion technology to lead them into the path of a train like he did with Spider-Man, he instead has a henchman drive them onto a bridge and leave them in the path of his next Elemental attack. Because absolutely nothing is forcing them to stay on the bridge, they all casually walk off the bus and out of immediate danger. It is unfathomable that a man as intelligent and resourceful as Beck would take such an idiotic approach, especially considering all he had at his disposal and how desperate he was.
Suggested correction: He wanted it to seem like they were killed in the Elemental attack because it was cleaner. If they were killed by a drone it would be much more suspicious than being killed in the disaster. Once the plan goes wrong, he does simply send an Edith drone after them. If it wasn't for Spider-Man's timing, he would have been successful as well.
But that is the major problem, and why I think it was an egregious mistake in the movie. The plan "goes wrong" because it was idiotic. So idiotic that it is unrealistic that Beck, a highly intelligent person, would have made such a glaring oversight. Leaving the kids on the bridge but not trapping them at all allowed them to make an easy escape.
I think the point is that Beck thinks he is the smartest person in the room and that this plan is going to work. Should he take into account MJ and co's free will, yes, but he is so maniacal (and not thinking rationally) that it does not cross his mind. This is proven by the fact that as his plan is failing around him that he still wants his suit pressed and ready to meet the Queen because it will work out in the end in his mind. Also, to your point, having them walk in front of a train or walk off the bridge, would not make him a hero. He needed real casualties and Peter's friends were the place to start. Finally, in the sequence showing Beck and his team preparing for the attack, he was focused on the theatrics of the attack and, again, thought the size of it alone would work (he wanted it bigger, scarier, more forceful).
Suggested correction: Fury is well aware of the drone system (he berates Peter for misusing it earlier). If Beck simply utilised EDITH to kill the students, it would give away that Beck was using the drones for his own gain. Once Fury was dead, he could have used EDITH had the original plan failed, but he certainly couldn't do it until after Fury (and potentially other SHIELD agents) had been taken out. He was going to attack London no matter what, so he took the opportunity to take out Ned, MJ and Betty at the same time.
This doesn't stop him from using a targeted drone strike to kill the kids, he was planning on using it to kill Fury anyway. The fact that he fails in his strike against Fury is irrelevant to the fact that he needed those kids dead and decided to take a round-about way of accomplishing this goal. Again, he doesn't have to use a drone strike, he is perfectly capable of using the illusion technology to force the bus off a cliff or into some other immediate danger. Having a henchman drive the bus to a bridge and hope the kids are dumb enough not to escape danger when literally nothing is forcing them to just stand there and be killed is ridiculously idiotic.
Suggested correction: Characters, even intelligent ones, are allowed to make bad tactical decisions. Real-life history is replete with examples. Just because it seems unlikely doesn't make it a plot hole.
True - this was originally submitted as "stupidity", which is slightly different, but this seemed like such a massive oversight that it qualified as a plot hole.
Suggested correction: Beck's intentions were to make it look like the kids were killed in the attack by the monster. Had he just killed them with a drone out right, it would have obviously looked like murder and foul play bringing in more investigations and potential problems for him.
But again, he doesn't need to use a drone strike he can use the illusion technology to trick them into an accident. Even what he chooses to do (just leaving them on the bridge) would have also been fine had he trapped them there at all. Just leaving them there without trapping them is so stupid it is unbelievable. It's like leaving someone on train tracks but not tying them up.
Suggested correction: He was an insane person and wasn't thinking fully rationally.

Stupidity: The commando mission to save Chewbacca starts gunning down a few Stormtroopers in the hangar. The heroes then go on leaving the troopers lying down on the floor in front of the ship, in plain view. They don't hide them nor ask the droids (who have enough strength and tools to pull them in) to, in fact they tell them to stay put. No wonder they are found out later (after a ridiculously long amount of time).
Suggested correction: Hiding the bodies would have been a waste of time, anyone who came to the hangar would immediately notice that the guards stationed there were missing and there was now a strange ship parked there.
The droids have all the time in the world, and people just passing by are "more immediately" bound to notice corpses in the middle of a hangar rather than possibly maybe question the fact that you don't see guards in that part of the hangar or investigate the ship - which could approach without anyone taking exception by appearance alone. At least remove the bodies directly in front of the damn ship!
Why would they be more likely to notice dead guards than no guards?
Anyone passing by might well thing the patrols were just out of sync, or a shift change. Sure they might investigate further, but they might not bother. Whereas a couple of dead bodies? Immediate red alert. Worth taking 30 seconds to hide them, surely.
Perhaps, but then it's made irrelevant 1 minute later as Finn and Poe run down a hallway blasting about a dozen stormtroopers.
For that matter, 1 SECOND later they kill stormtroopers in the far part of the hangar. They are killing people all over the ship during their mission and it's not like they hide every single one of them, but they leave two bodies *exactly* in front of their ship (and telling the droids to stay put). You can even see later that there is a stormtrooper with his weapon pointed exactly where those two corpses are, with the 'smart' commanding officer asking "whose ship is this?" at the sight of that. Maybe I am spoiled by a trope here, but it's the first time that I see someone in an action movie leaving corpses right in front of their only escape route/vehicle, that's so counterintuitive. (Did they even have an escape plan, actually? I don't like hypotheticals, but gee, if only she did the Jedi mind trick thing to those 2 guards who came over to inspect the ship instead of doing it later. But I digress).

Stupidity: When Colonel Hardy is about to crash the ship he's flying into a building, Faora sees it and she has more then enough time to leave the ship and get to safety, but she does nothing and just stands there.

Stupidity: Why, in the most secure computer room you could find, with all those detection devices, did they not install video cameras? There is no risk of a security breach as they could be locked into a position that would not show the computer screen or keyboard but would show that an intruder had entered the room.

Stupidity: When the crew of the German U-boat boards Katanga's ship, the submarine moves in a position perpendicular to the ship's bow as if to block its path. In reality, this would have been a pretty stupid move by the German captain, as Katanga could have rammed the submarine easily. Any kind of damage to the hull, especially ramming damage (even from small ships), would have been catastrophic to the submarine. It makes no sense to make a manoeuvre like this.

Stupidity: When the Keymaker is closing the door to the room that leads to the Source, he stands in the doorway resulting in the multiple Agent Smiths gunning him down. He could have easily closed the door without standing in the doorway and consequently would have lived.
Suggested correction: Who says the door was bullet proof and the Keymaker couldn't have been shot through the door?
The point of the stupidity is that he shouldn't have been in the doorway at all, even if the door wasn't bulletproof, there was no need for him to even stand behind the closed door. He could have pushed the door closed from the side.
It seems to be a heavy door, he simply couldn't close it with just his arm, thus he had to move his body forwards in order to close it. In that brief moment he got shot before the door closed. He could have for example kicked the door shut but he simply didn't think of that at that moment, also not knowing the Smiths were about to fire a volley of bullets at them.

Stupidity: After stealing the taxi, Cassandra removes the license plate, and yet the taxi's identification number is located in bold plain sight on the doors and roof light.

Stupidity: At the beginning, young Indy knocks out the driver of the car, pulls him out, and just leaves him on the ground by the car while entering the car. Neither the knockout nor the unconscious driver lying around are noticed by any Germans in the vicinity. Not even by the soldier who opens the car door and the officer who gets into the car, both of whom immediately appear after Indy has gotten into the car. (00:06:00)

Stupidity: When Elena first sees the huge honeycombs in the giant beehive, she tells Herbert that they cannot possibly be honeycombs as they are much too big. Considering she spent the morning watching pitched battles with a crab the size of an elephant and a five meter tall baby bird, don't you think she might have grasped the concept of giant animals, birds, and insects by that stage?

Stupidity: Bori Khan is a skilled archer and a man without honor. He's not fighting fair, and cares just to win, as established and explicitly said. He shoots an arrow at Mulan, the Witch gets in the arrow's way sacrificing herself to protect her...and for no reason whatsoever he does not shoot anymore, giving the chance for the two girls to share their very special dramatic moment together, but creating a colossal plot contrivance. It is a know movie cliche for the fight to 'pause' around the main character, but here we have a sniper who desists completely (he won't shoot anymore) for absolutely no reason. (01:29:00)

Stupidity: During one of the test drives, the hook that Hiccup uses to fasten himself to Toothless gets bent, so he takes Toothless to the blacksmith to cut the line. There are two ways he could have easily avoided this: He could just unhook the saddle, take that to the blacksmith and cut himself loose, or he could just untie the leather strap. What he does here is needlessly risky and just there for his awkward conversation with Astrid.

Stupidity: Monk steals the magazine from Coffey's SIG. However, I don't see how he could have jacked the slide to eject the round in the chamber without being noticed. Someone as paranoid as Coffey was at this point would not have left the chamber empty. (Just FYI, when you load an automatic pistol with a magazine, you have to pull back and release the slide to load the first bullet in the barrel.)
Suggested correction: Since we are never shown that Coffey did chamber a round, we cannot assume that he did based on his personality alone. Therefore this isn't a plot hole. However, it is ridiculous that he is threatening people with a gun without a chambered round. This entry should be listed as "Stupidity."
SEALs don't carry weapons without a round chambered. The "maybe" here falls much more on the side of the round being in the chamber. And "Stupidity" wasn't an option available when this entry was originally submitted. :).

Stupidity: Reliant's prefix code is 16309. This code prevents an enemy ship from ordering a friendly ship to lower its shields or something similar. Five digits with no symbols. We know that symbols and letters aren't used since Spock uses a 10 digit set of switches to input the code. This is ludicrous. In 2016, a high powered server could crack a 6 digit password in approximately 0.0224 seconds (at 100 billion guesses/second). Any starship computer would have to far more processing power then a 2016 server. The prefix code protecting a starship from cyber attack would have to be insanely complex in order to be useful.
Suggested correction: Keep in mind the era that this movie was made in. This movie was made before PCs really existed. Computers at this time were typically huge devices or box like containers. Their data storage capacity was minuscule and there certainly wasn't any form of AI logic programs built to "hack" passwords. I know this movie is about space and set in the future but there's a lot of stuff in Star Trek movies that based on our technology or development currently, we would expect something bigger, smarter, etc. We still have problems today with people using archaic password structures like 1.2.3.4. or actually using the word password for/in their password. Back in '81-'82, I'm sure that most people would not have thought about codes being hacked. This is not to mention that in many movies, which I don't know if there is a specific reason for using 16309, codes, passwords, numbers for addresses/apt#/room#/etc and other info frequently come about as tribute, honoring, or coming from something in the lives of a film's director/producer/actor/etc! So sure with today's technology, which could have been accomplished more than 10 years ago as well, using a single string of numbers as security measures for anything is foolish and can be hack by a self running password-like cracker program... But they made this "code" back in the very early 80s when computer hacking was barely unconscionable (MAYBE) so unless these #s were a tribute or to honor something, I'm pretty sure no one was even thinking of hacking back then... We all aware of today... all about the hacking threats and YET we still have people using 1.2.3.4., the word password, or other horrible predictable password choices that can easily be broken by a password cracking program... And we know that there's a huge hacking threat requiring strong security measures but don't do so while back then, there was little awareness of the threats of hacking much less the concept of hacking altogether.
OR... in this future they have limited the number of password attempts to one a day and the ship automatically goes to red alert after a failed attempt until the right code is entered. That way it would take 7,327 years or so to try all the codes with the crew on notice and plenty of time to address the threat.

Stupidity: Oddjob brings the crushed cube of the Lincoln back to the stud farm so that Goldfinger can "separate my gold from the late Mr Solo." Oddjob could have simply removed the gold from the trunk of the Lincoln before having it crushed.

Stupidity: When Jasmine finds out that Prince Ali is actually the boy she met in the marketplace, she seems to completely forget about Jafar telling her he had been executed. She never asks why he's alive, nor does she even bother to confront Jafar about his treachery.
Suggested correction: The fact Aladdin was alive only told her Jafar lied about it. When she is brought back by Aladdin to the palace it is still night, not long after that she is confronted by her father and Jafar who has him under a spell. She hardly had time to ask about the treachery, probably thinking to do it in the morning. It is there and then Jafar is exposed by Aladdin. She probably wondered about it, but didn't figure out the implications yet.

Stupidity: When the invasion of planet P begins, we see the Rodger Young get hit. In the explosion sequence, we are treated to people sitting around tables in what can only be described as a mess hall exploding. In a military environment, this would be a time where everyone would be at their "battle stations". Nobody would be having chow or off-time when the ship is expecting combat. In this case, it was a planned troop landing.
Suggested correction: Yes, it was stupidity, but it was an intentional depiction that supports the plot. During the landing, the Captain is completely surprised by the bombardment and says something like, "This isn't light uncoordinated resistance." The fleet's lack of preparedness at Planet P is a major plot point that later results in the replacement of the Air Marshal in command.
No, you are talking about a different sequence. When they are unprepared, they are doing an invasion of Klendathu, the Bug's home planet. This is earlier in the movie and the Rodger Young was only slightly damaged in that. The stupidity is about the invasion of Planet P at the end of the movie, where the Rodger Young is cut in half.

Stupidity: When Han tells Drydon Vos that he and Tobias will steal unrefined coaxium from the mines on Kessel, Vos initially says no, as Crimson Dawn's relationship with the Empire would be at risk. Han then explains that the Empire wouldn't know they were working for Crimson Dawn. Vos then agrees but insists his top lieutenant Qi'ra accompany them, even though she is a known associate of Crimson Dawn and literally has their symbol branded on her wrist.