Stupidity: After pushing the button for the outer door in the airlock, Justin was brought out of his trance. The door was on a delay, so why didn't he just go to the console and abort the door's opening?
Stupidity: The supposed criminal mastermind had exactly what he wanted right at the beginning; all he wants is killing the girl, and he knows (he says it himself) that he is facing just mall cops who carry no weapons. But he utterly wastes for no reason the 'first contact', when his intentions are not known to the occupants. If only he had a gun, or brought along a guy hiding a weapon instead of 'suitcase full of bribe money dude' (which only shows how easy it would have been for him to have backup), he could have easily killed everyone through the doors when they were sitting ducks, with no fear of retaliation whatsoever. Nobody as ruthless and daring as he supposedly is, would show up unarmed for no reason.
Stupidity: This lady lives in the United States, she obviously doesn't have a criminal record, she can go buy a handgun or rifle, heck she can buy a handgun and rifle and extra magazines and ammo to defend herself, but she chooses golf clubs and baseball bats and mace. (00:00:01 - 01:20:00)
Stupidity: When Bobbi Jo sees Ash's severed possessed hand holding her hand, she freaks out and runs out of the cabin and then gets killed by possessed trees. While it's certainly natural for her to be terrified, why would she run AWAY from where all her friends are and go off by herself?
Suggested correction: She is a civilian in a blind panic, and even people with actual training have done dumber in panics (e.g., choking firefighters run away from other firefighters who could help them). She also has no idea how dangerous the woods are at this point; she walked to the cabin just fine and only saw scary things inside it, so she thinks she'll be fine if she just runs from the cabin.
Stupidity: The first time they go into Butler's garage next to the prison they are breaking in, but Butler never witnessed any break in clues to raise his suspicion. They replaced the lock with the exact same lock. It is clear that they didn't know that this was his access point to the prison, but once they found out there is no way to cover up that someone compromised the facility. How is Gerald sure that the bomb will remain under the meeting room while on his way back to the cell? He has a camera in the meeting room but in the bomb room he didn't bother to put one.
Stupidity: When the two Russians are walking past the security guard after killing Gregor, they are just allowed out without being detained because one of them shows a Chilean passport. The French gendarmes are not that incompetent. They would detain the men until everything is (or is not) cleared up. (01:49:05)
Stupidity: When Liz sees the dead deer blocking her lane, instead of merely going around it (using the opposing lane on a rural road without jeopardizing her safety), she exits her vehicle - leaving her three-year-old daughter unattended in the back seat - to "look" at the deer. This furthers the plot by giving the "werewolf" opportunity to attack and kill her... as well as her daughter Miley. (00:42:35)
Stupidity: After the cloth was lit, the "Santa" could have easily thrown the Molotov Cocktail far enough to ignite the Christmas tree but, instead, casually walked to get closer (within several feet) before tossing it. This may have been for dramatic purposes, but carrying a lit rag (part of a Molotov Cocktail) unnecessarily increases the risk of getting a burn injury (which can be quite serious/painful). (00:02:35)
Stupidity: Mason should have also removed the other gun he had in his office for display, or he could have removed the bullets from the guns. There is no reason he would have to use these guns for his victims, so it makes no sense to leave the other gun in his office or have them loaded with bullets.
Stupidity: If the doctor was able to choose the people to go on the helicopter, why didn't she make up a reason to put the president's son on the helicopter for his safety? She could have said he was sick. (01:14:40)
Suggested correction: He is shown to be a caring person. There is no way he would take the place of a sick woman or child just to save his own neck.
That correction is illogical though. By not getting on the helicopter he puts everyone else at way more risk. It would have made getting the rest of the people left behind out of danger much easier as they wouldn't have been hunted down by the people who were chasing the president's son. By not getting on that helicopter he could have gotten everyone killed.
Stupidity: After Jack is found not guilty, you would think the first thing he would do is to get rid of the typewriter he used to send the notes to Teddy to manipulate her into winning the case for him, especially when she is sleeping with him at his home. Not to even mention the fact he hid the typewriter in an unsecure manner in a closet behind a stack of towels, a place where it would very easily be found. This foolish mistake exposed the truth to Teddy and cost him his "freedom."
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: After Corinne Dufour realises that Drax intends to have his dogs kill her, she inexplicably attempts to flee on foot, running right past the golf cart she arrived in. The golf cart would have given her more speed, range and protection, and would have been a much better choice for fleeing.
Suggested correction: Golf carts are very slow, and are open on all sides: the dobermans would've easily dragged her off it. The biggest stupidity here is that she should've fled to a crowded area with other people instead of the woods. Then again, she was panicking, and not thinking straight.
Stupidity: Peter and Amanda were wealthy enough to buy the 11th floor penthouse for $579,000 but had no security cameras. Also, Det. Martinez never thought to check surveillance cameras outside the Wright's penthouse; surely cameras were around and/or the Detective could have questioned neighbors if anyone saw Charles near the penthouses or with the Wright's dog Humphrey. Peter or the detective could have gone near Charles' boat without a warrant and called Humphrey to see if the dog barked in response.
Stupidity: Four H.S. seniors are sitting in an SUV. A storm quickly intensifies and Billy gets out of the back seat to get a better look (wipers are on "fast"). Seconds later, Billy spots a tornado coming. Marcia (driver) tells Billy to "get in." Needing to flee the fast-approaching tornado, Marcia wants to leave as soon as Billy is in the SUV, so she yells, "Billy, get in!" The tornado is feet away when Billy closes the door - whew, he's safe! Marcia STARTS the SUV when the tornado starts bashing it. (00:01:14 - 00:01:38)