Stupidity: Dafoe does a lot of looking around while flying the plane. He could have pulled up much sooner. Then he screams and puts his hand to his face, and then he sees the tower and crashes into it. (01:53:29)
Stupidity: Liv and her five friends went to Willy's to set it on fire, but Liv insisted they first go inside to get the Janitor out. All were aware of the situation and danger related to the mass murderer and the animatronics, but Bobby and Kathy went into another room to "hook up." Kathy recognized the room as the one where the killers committed suicide and later saw movement, but she continued having sex with Bobby until he was attacked and killed. (00:38:48 - 00:42:02)
Stupidity: Alex, a contract killer, went to the hospital to kill a patient. After parking in the hospital garage, Alex put his car keys under the sun visor, risking the possibility that his car could be stolen. When Alex returned to his vehicle, the keys were not there. A professional or expert assassin should take precautions to assure his getaway car will be there and keep his keys on him. (00:01:45 - 00:04:30)
Stupidity: Why didn't they take out the crushed hand guy while the creature was fumbling inside the glove? Plenty of time to do it. Why did no one use a knife to stab the creature?
Stupidity: Why would 006 put Bond in a self destructing helicopter instead of just shooting him? Being Bond's old partner, he of all people should know how good of an escape artist Bond is.
Stupidity: All that chaos going on at the end of the movie. Gun shots. Screaming. Blowing up police cars. Yet not one neighbor comes out to see what's going on.
Suggested correction: Gunshots and explosions going off at a neighbor's house isn't going to make me go and investigate. It's going to make me call the police and hide in my own house.
Stupidity: In the freezer you can see the electrical wire power cord that is powering the motor on the wall. She could have easily pulled/ ripped the wire to stop the freezer from working. And when the chemical bomb is in the mixer they could have unplugged the machine which would stop it from going off.
Stupidity: When the birds gather in the schoolyard, Melanie runs in to warn Annie. Rather than calling the police or fire department for help and then shelter in place until aid arrives (which would take about ten minutes), they instead decide to make a run for it with the children, out in the open, getting attacked by the birds. As it's the 1960s, the schoolhouse presumably has a working phone.
Stupidity: While Mr. Butler was upstairs taking a shower, Lucas goes into his house, kills his wife, and takes the baby to the school (into Mr. Butler's classroom). Lucas wanted to take away Mr. Butler's family, so all he needed to do was also kill the baby at the house (or leave the dead baby outside on the porch for Mr. Butler to panic while searching). Lucas could have left the house without getting caught for committing a double murder; instead, he keeps the baby alive and assumes Mr. Butler will know he took the baby to his classroom. (01:17:53)
Stupidity: Vincent's choice to cut the power to the building that Annie is in does nothing but waste enough time for Max to save Annie. It would have been easier just to go up to kill her and he probably would have gotten away from the police if he did so.
Suggested correction: It also slows Annie and Max down by forcing them to walk in the dark, and also, at this point, Vincent is really torn up from the crash, and the mere sight of him is going to make Annie very suspicious or even afraid, unless the power out (which for all she knows is just from the building) gives him a plausible reason for being so mauled.
Stupidity: Why did the bad guys even go for Xander as he was snowboarding down the mountainside? First of all, it was impossible for them to even get to him as the mountainside had several cliffs. Secondly, why did so many go? Wouldn't it be clever to have as few as possible leave in case his snowboarding was simply to draw attention away from an ambush? They knew he was an agent by now and should know he could have gotten reinforcements. Thirdly, they could just have simply waited for him to get to them.
Stupidity: The protagonist with her kid stops a car with two guys, in the middle of the night in an isolated country road. Both the adult and the kid scream that a dangerous maniac is chasing them. So naturally, the two guys (who do believe them, it's not that they are being dismissive) offer them some hot coffee, and they drink it right there in the middle of the street, not dialling for help, getting in the car to drive away or anything, because that's what normal people do when you tell them a serial killer is nearby; stop for a hot cuppa.
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: Captain Poison has a fairly good idea of where Solomon buried the diamond. We know this since when he leads the captured Solomon to the spot, there are already several holes dug looking for it. Despite knowing roughly where the diamond is - down to a relatively small area - he makes no serious effort to excavate the ground, instead contenting himself with a handful of incredibly shallow holes.
Stupidity: After one of the policemen decides to jump over the railing and right into the angry mob (!), Arthur just easily sneaks by ducking under it and takes a nice stroll that will lead him through an unlocked door. Nobody in the mob he is part of decides to do the same, and you can also see that one of the policemen is turned towards him, but does not even yell at him or move. And of course, with the theater packed with the Gotham elite basically under siege by a mob and guarded by the police, the door is unlocked and unchecked. Why not. (01:02:55)
Suggested correction: The point is they were all too distracted by the tussle to notice Arthur ducking behind the barrier. No cop sees him. The angry mob is controlled by the barrier and not all that large so they haven't taken extra precautions to keep the mob at bay, yet. The door Arthur gets in is probably a fire escape and can't be locked for safety reasons.
I think that with an angry mob worth putting barriers and a big police dispatch, they'd tend to lock the door that is like a 20 feet of walk in a straight line. I mean, they have barriers in front of the stairs, but at the base of the stairs there's an unguarded, unprotected, unlocked door. It's just funny. Not even something in the back or around the corner, no; literally one step to the right of the blockade.
Stupidity: Why weren't any of the guards thinking of running to the base of the crane to stop it? Surely there was a more than fair chance to capture Frypan as he had to stay up there and swing the bus to outside of the wall and lower it. Not only does that take a long time, he had to climb back down again.
Stupidity: The guy who offered to help Rachel go to her car at the gas station and get away from road-raging Tom walked directly in front of the path Tom would be taking to leave. When the guy realised Tom was going to run him over, he went onto the road instead of toward the store where he would be safer. Also, the guy - knowing Rachel's situation - foolishly told Tom that he got his plate number, which served to aggravate Tom into driving into him. (00:32:15)
Stupidity: The prison where Magneto is held should have had a contingency plan just in case of escape, like machine guns outside the cell, or tranquilizer darts, or gas.
Suggested correction: What good would machine guns and tranquilizer darts be against a man who can literally control and manipulate metal? As for gas, the area outside the cell is so large that any gas would quickly dissipate before it could be effective.