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: Robocop is just about to be unveiled to the press for the first time, and they decide right beforehand is the perfect time to upload a massive amount of data, including his own attempted murder. Then, they seem shocked when that causes problems. No reason to do that right before a very public, time-sensitive moment except for the sake of the plot.
Stupidity: The train which takes M from New York to London arrives looking like an old tube train, then when she's on board converts into a high-tech train, to her amazement, and whisks her across the Atlantic. Except...why did it ever look like a regular train? She's in a MIB station, it's only used by agents and aliens, it goes to another MIB station, and when it arrives and people get off / on before it continues its journey, it stays in its high-tech form anyway.
Stupidity: As Powell was standing at the completely wrong "eye" in the temple to begin with, all Lara had to do was say nothing of his mistake, he'd never had got the first piece of the triangle to begin with, world safe for another 5000 years.
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 Susan is on the balcony with the man trying to kill her, she pulls out her gun with one hand (she's leaning on the other hand). He says she won't shoot because the gun's magazine has fallen out and Susan gives up and drops the gun. However, if there is a round in the chamber, the gun can still fire without a magazine in it. As trained as Susan is suppose to be, she should know this. But, if there's not a round in the chamber, then, as a trained agent, Susan is ineptly prepared to use her gun. If there's not a round in the chamber, pulling the trigger will not fire the gun nor will pulling the trigger chamber a round. But she would need both hands to chamber a round and she only has one hand free. There is the occasional gun that has a magazine disconnect safety, but it would be stupid for field agents to have one since they may be in a situation where they need to fire without a magazine in (such as this situation).
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: When the shuttle arrives with the assassins, O'Niel is shown loading a shotgun, then he carries that gun when he runs to his office. When he leaves his office again to confront the assassins he grabs another shotgun from the locker. Why didn't he just grab the gun he walked in with?
Stupidity: When the saw yo-yo comes down for the third time, Bond grabs the cord to pull the wielder down off the gallery. That was, when you think about it, a patently bad idea. If the yo-yo hadn't become stuck in the desk, Bond would be collecting his fingers in his hat (note that the blades are still spinning as Bond grabs). (01:15:45)
Stupidity: In the opening scene with the military convoy, the two soldiers in the lead vehicle never notice the car veer into their lane, even though their faces are bathed in bright light from the car's headlights. They simply ignore it and keep talking to one another.
Stupidity: At the very beginning of Donnie Yen's fight inside the CIA conference room, security barriers start descending in the room, windows first and then doors, but somehow the exitway for him (which even communicates with the main elevator. Not a secure bunker or anything) starts shutting down a minute later so he can baseball slide past it before it closes. That's pretty nonsensical security protocol. In fact, the whole operation is successful because apparently the CIA Headquarters lack any cameras and sensors in the corridors, security at the lower floors, main doors, perimeter, especially during the top brass meetings (that happen in a room with huge windows with reinforced glass a man can break jumping at it). (00:09:20)
Stupidity: They go to great pains to lock the nodes behind an explosive lock, then have a debate about whether Riddick's somehow broken in. They eventually unlock them, check they're still in place...then just leave the locker completely unattended and unlocked while they discuss plans, and Riddick of course steals the nodes.
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 the scene when the cook is torched, why didn't he just jump out of the longboat into the water? Why get burned?
Suggested correction: It would be pointless. If he ran away, Blackbeard would just come after him and make him suffer greatly. At least the fire is quicker than torture or being zombified.
Hogwash. Fire is even more painful than torture.
Not only that but, it's only speculation what would Blackbeard would do to the man if he had survived.
Stupidity: When Stuntman Mike is taking photos of the girls, he is shooting with the lens cap on the camera.
Stupidity: There is no reason why any person as intelligent as Janet would keep the knowledge of Kang secret from her family. The extended Pym family are the only people in possession of the one thing Kang needs to escape. The brief explanation she gives is that she wanted to protect her family, but this makes absolutely no sense whatsoever, and she makes no attempt to explain how this secret keeps anyone safe.
Suggested correction: She is obviously scared out of her mind concerning Kang. She, through her fear, had hoped that him being trapped in the Quantum Realm would stay permanent as long as nobody knew about it in the normal universe. In that way, she tried to protect not only her family but the entire universe.
Not only does she not say that she is "scared out of her mind", she also doesn't act like it either. There is no indication that she is so frightened by Kang that she has lost her senses - quite the opposite, actually. She appears to function rationally and intelligently in every other area concerning Kang, except of course for simply telling anyone how dangerous the Quantum Realm is because the movie wouldn't have a plot otherwise. It's pretty egregious and wildly ridiculous.
Of course, she doesn't say that or act like that. But what she saw of him, when she touched his ship, scared her enough to go to all that trouble to keep him in the quantum realm at all costs. She thought it would be safe to leave, that he was trapped forever. Her judgment was wrong, probably caused by her fear. She is only human.
"Fear" is not enough to get past this level of stupidity. My point is that she doesn't act so frightened; she isn't irrational in any other way. It's just a flat-out, stupidly written element of the film that is impossible to believe. There is no way on God's green earth she should keep this secret, even after her family has made it to the quantum realm. I get that the movie is trying to say she is frightened, but this goes well beyond making any kind of sense at all; it's ridiculous.
Part of the stupidity also involves Janet's action in the mid-credit scenes of "Ant-Man and the Wasp," where she actively helped send Scott into the Quantum Realm to get quantum energy. If she was so afraid of a signal being sent to the QR, she wouldn't have let Scott go without explaining the dangers of going. This film seems to ignore that and instead seems to focus on Janet simply not wanting to discuss her involvement with Kang and her guilt, thinking no one would go back to the QR.
Stupidity: Howard has the opportunity to shoot Jack at the end, but doesn't for no discernable reason; he's already committed multiple felonies, and shooting Jack would help cover his tracks all the better. In fact, he could even have just taken the cash onto the subway and left Annie behind while staying in full disguise as a cop.
Suggested correction: Howard Payne's taunting dialogue in the subway station suggests that he wants Jack to live a long life, tormented by the fact Payne was able to beat him. He doesn't become intent on murdering Jack until the dye pack goes off, ruining the money. After that, he tries to shoot Jack but runs out of bullets, then decides to beat him to death with the detonator but fails.