Stupidity: Shriek is being taken to a new facility for superbeings, after a medical exam established that her sonic powers that she has been using since she was a kid are too strong to keep her at the correction house. So "naturally" for this transport she is not gagged, sedated, not even bound, and there's just one guy with her, not even wearing earplugs. It couldn't possibly be any more comically unsafe.
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: 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: 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: We know that the two 'special visitors' have been in our universe longer than a day. Despite being capable, smart, heroic figures, they did diddly-squat until the plot says so, since they haven't tracked down the very public (they recognize them) partners of Spiderman, they don't show up for the battle broadcast by JJJ on giant screens, but more importantly, they do not know who the "Avengers" are, showing they didn't look into Peter's history - the name would have popped up in relation to Stark, the blip and much more. Seems that they didn't even try to look for him.
Stupidity: To save the people from rubble falling on their heads Flash does not move them aside like he did with his future love, but does some strange manoeuvre which takes seconds - since we see people moving normally - and happens in midair (how does he get there?) and that does not take care of a huge chunk of concrete which he does nothing about, shouting just "No!", but Cyborg has all the time he needs to load his Mega Man arm and vaporize it in midair. (02:00:00)
Stupidity: When the rebel leader talks to Rick Flag guaranteeing her help, she mentions that she will help to find "this Gaius Grieves", speaking as if it was someone unknown to her. He's been around the island (going to bars and surely not being reclusive) for 30 years; it's pretty difficult to think it would not be one of the most known people on the island, given his role, unique appearance and the small community.
Stupidity: After the fight in the woods Bond walks back a long way, instead of driving the Toyota he had left in the forest in full working order.
Suggested correction: The Toyota has had a major chase over very rough terrain, it may no longer be operable.
It was operating fine when they stopped it in the middle of the forest.
Stupidity: Arishem's plan with the Deviants hardly makes any sense; he sent out biological beasts that he can't control, to kill off the natural predators of every planet. Forgetting the fact that obviously it didn't work (but the movie does not say that) because Earth has always had predators, that's a terrible plan to begin with, since any ecosystem needs predators or the other animals will grow uncontrollably.
Stupidity: Natasha is in Norway on the run - Norwegian radio mentions her by name, Yelena talks about her being on magazines, she's very recognisable, and yet she goes into a gas station with her sister without changing her appearance in any way, and loudly talks about being an Avenger and killing people, right in front of the gas station attendant who for all she knows would be on the phone to the authorities the second she's out the door.
Stupidity: When the crew think that Dorothy is a robot with a bomb planted in her and is capable of exploding, they begin to think that she is about to explode and attempt to dodge it. Rather than hide somewhere or take cover behind an area that may protect them, they just get down on the floor in front of them and cover their heads with their hands. If they thought the explosion was going to be as deadly as the one they saw on the news, this method of taking cover wouldn't be even remotely effective. (00:24:40)
Stupidity: After the Sheriff was shot in the neck but was able to run into the woods, he hid behind a wide tree trunk. He shot at the Virtuoso but missed. Instead of staying behind the wide tree trunk and shooting again as the Virtuoso advanced toward him, he flees from tree to tree where the trunks are not as wide, giving him less protection and more of a disadvantage. Eventually, he is killed by the Virtuoso. (01:21:48 - 01:22:26)
Stupidity: For someone trained like "H", it was absurd that he would run down the center of the road toward masked gunmen and get shot multiple times. It was also ridiculous for him to have taken his son to a location that was potentially dangerous and put him in harm's way in the first place. (01:13:20)
Suggested correction: I'm not sure how much H was trained. If I recall correctly he's a skilled criminal, and all his "training" was faked so he could get the job with the company. Regardless... training or not, all that goes out the window when your child is being attacked. Paternal instinct took over and he was rushing in to protect his son. As for your 2nd point, it's made clear that his task was to simply stake out what was supposed to be a routine truck route. They had no idea the truck was going to be robbed.
Stupidity: Ben is standing behind Marley with a gun to her head as protection against Aaron, who is pointing a gun at him. Aaron shoots Marley and Ben just stands there, first looking at Marley on the ground then looking at Aaron (standing about ten feet away). Aaron screams and shoots Ben in the abdomen. After Ben falls, Aaron shoots three more rounds at him but misses. Ben is also able to stand and walk around despite his abdominal wound. (01:17:30 - 01:20:40)
Stupidity: When the thunder/lightning starts, Hannah correctly tells Connor "We gotta get downhill." Then she tells him to run and stop, plus shows him to crouch down. Granted, they needed to act fast, but her instructions were poor for someone supposed to be trained in safety. Crouching should not entail placing one leg from the knee down onto the ground - only the balls of the feet should touch the ground and the heels should be together. She didn't tell him NOT to lie down, but he was when he fell. (00:53:14)
Stupidity: David and his partner Cal drive into a weeded area near the garage/warehouse the drug bust is going to be made. David says, "This might go south. We need backup." David and Cal sit in the car talking about not letting the product get onto the street where someone might die, etc. then exit the vehicle without calling for backup, which could have been done in a few seconds (and should have been done as soon as David said they needed backup). (00:02:10 - 00:02:37)
Stupidity: The "body armor" General Ford and others wear is very bulky and appears to be quite heavy with all the attachments (e.g, flashlights on shoulders). With the protective suit protruding perhaps 8", it would most likely restrict/slow movement, contrary to what soldiers need. Moreover, the body may be protected, but there's no protection for the face/head, leaving them exposed/vulnerable. Today's products tend to be lighter, thinner, and stronger, so would be expected in the future.
Stupidity: Two oil rig workers were looking at two young ladies in bikinis who were sunning themselves on a boat/yacht. One oil rig worker said, "That's where we should be right now. With them, enjoying the sun, instead of baking in it." Both men had double layers on - a jacket or sweater over a jersey or T-shirt - and one man was wearing a tossel cap. Even if it gets cold on the rigs at night, they did not need to be dressed in warm attire during the sunny daylight hours. (00:10:35)
