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: 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 Casi changed the tracker on the Navigator, he was sneaking between vehicles to get out of the tow pound. The Whale came and stood in front of the two vehicles Casi was between. Casi stood up and, instead of turning around and running away, rushed TOWARD The Whale in an attempt to get past him. The Whale, much bigger, threw Casi against a vehicle and then onto the garage floor. (01:03:34).
Stupidity: Patrizia Reggiani is no rocket scientist in this movie, but it's quite bizarre that calling the fortune-teller she sees on TV, with her name written in giant letters in two different spots on screen, she asks her "What's your name?" It makes sense for the international audience who may not recognize the word "Pina" as a name, but an Italian wouldn't have any doubt. (00:41:05)
Stupidity: Instead of breaking into Gordo's house, covering all the furniture in one room with sheets/thin blankets, and waiting for Gordo to return home in order to kill him via a "dramatic re-enactment" (in an adjacent room which was not shown to the audience), Bill could have taken Gordo anywhere to avoid getting caught or calling the police on himself. Had Bill taken Gordo to his already-"wrapped" motel room, he had enough injuries after the fight to claim self-defense against an intruder. (01:43:20)
Stupidity: For claiming to know how to deal with Music Ebo doesn't do a good job. He wrestles her to the ground to calm her down which is very dangerous for both the patient and the caregiver. It's only recommended as a very last resort and in both scenes with this neither one required it to be used.
Stupidity: While awaiting their flight home, Nancy told Teri, "Think I miscalculated the tea. I'm not gonna last three-and-a-half hours [on the non-stop flight with no restroom facility]." Nancy then went into the gift shop where Stuart Couch introduced himself, asked if he could get her a drink, and bought her a bottle of beer. Nancy drank at least some of the beer on screen, even though she was already concerned about drinking tea before her flight. (00:59:28 - 01:00:30)
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: Colette was holding the metal ladle close to the bottom of its long handle and near the top of the hot pot of stew she was serving, and yelled, "Ah." due to her hand getting too hot. She had a towel wrapped around the handle of the pot, but it was that hand that got too hot/burned (not the hand that was holding the metal ladle close to the top of the steaming hot pot of stew). (00:04:48)
Stupidity: Gunner [Director and Co-Writer Brock Harris] was given a puppy ("Barnaby") by the nurse (?) who told him he was sorry his "[VA] benefits didn't go through." Gunner could have merely refused to take the puppy but, instead, drove away with it - and later threw it out his truck's window while he was driving. (00:24:42 - 00:25:55)
Stupidity: Two things: 1. I find it inconceivable that there is only one Carbon Dioxide Removal Assembly (CDMA) and no spares for a two-year mission. 2. The crew has 20 days to fix an oxygen problem. The commander decides on a 10-day window. 5 days into that window they try to load oxygen from the Kingfisher spacecraft. One is lost into space. Zoe decides to go and fill the other one in the midst of a solar storm that will only last hours. Why take that chance? A few hours wait is still quite possible.
Stupidity: Lyla does not like the idea of Mickey fighting and initially does not want him to agree to the fight. Lyla eventually tells him "okay", but he must stop when she tells him to stop. This may give her a reason to go to Dubai, UAE with him, but she is about 8 months pregnant. An international flight has some risks plus she would be far away from her OB-GYN doctor if there were a complication. She should have had enough sense to avoid international flights/traveling so close to her due date.