
Stupidity: The crack house workers are all topless to prevent 'hiding' any product for personal use. Yet are also wearing parachute type pants that they could easily hide things in.

Stupidity: Judy Hicks, a trained cop and sheriff with over a decade of experience, does not carry a back-up holstered gun on her when she is off-duty, one day after her son's close friend is stabbed seven times near to death. A trained police officer/sheriff would also question why the killer would tell her they are about to kill her son, before they do it, if not to bait them and lure them into a trap. (00:45:58 - 00:46:30)

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: As soon as Bundy got into the building (instead of when he was still outside), Kaminsky asked him for a "camera check." Bundy had a yellow button with a big star in the center pinned to his jacket's right lapel. Bundy put some fingers next to the button and raised his lapel with the others, making it obvious he was wearing a camera. When Manson got into the lobby (area likely to be under video surveillance), Reese (who saw Bundy and Manson outside) came into the building to give them weapons. (00:03:50)

Stupidity: When the police turn up the first time the mother lies to them to get them to go away but the burglars can't hear the conversation. She could have told them exactly what was happening and that she had to make it look like she'd got rid of them. She could have then smashed all the cameras and just let them in.
Suggested correction: This was a character decision, and a completely understandable one. Her daughter was being held hostage in the panic room. She decided to cooperate with their demands for the safety of her daughter. Your idea is a solid one, but she simply did not think of it in her state of mind. She opted to get rid of the police, and her decision is not a movie mistake.

Stupidity: Despite being assaulted by an intruder that she managed to temporarily fend off, the female neighbor takes forever to say something when she calls the police, which is just enough time for the villain to regain his senses and attack her with a huge drill.

Stupidity: This highly trained squad of soldiers is sent into a known contaminated zone with all manner of chaos going on within in...and the second one of them sees a woman outside his APC he ignores a direct order and pops outside to see how she's doing.

Stupidity: When he's using carbon monoxide to poison the corrupt detective Frank Masters, the windows in the car were operated by the key fob. Unusual, but OK. Maybe. But the detective could've simply opened the doors after McCaul left him in there. The door worked when he was forced into the car. (01:24:30)

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: How would a devout catholic like Angela not believe in the devil, as she tells Constantine? Makes no sense.
Suggested correction: Some Christians don't believe in the literal personification of the Devil. They see him more as a metaphor for all human sins. So according to them, the Devil is not something to blame evil on. Everybody has God and the Devil in them.

Stupidity: At the end, the police inspector talks Bruce Lee into surrendering, and about 8 people (including the inspector) escort him out of the school. As soon as they're outside, Bruce sees a formation of heavily-armed police preparing to fire. Realizing he was betrayed, Bruce Lee charges, screaming, straight into a barrage of gunfire as the action freezes for credits. However, before the action freezes, there's NO reaction from anyone standing behind Bruce Lee, even though they are directly in the line of fire. Even the police inspector (who knew the police gunmen were waiting outside) just stands there instead of immediately diving for cover.

Stupidity: Crystal knows she is being hunted and in a very dangerous life-threatening situation yet, after she kills "Ma and Pops" in their Main Street Market, she grabs only a few shotgun shells out of the open box instead of taking all of them or as many as she could find. Also, she walks some distance to the store but did not take anything to drink or eat. (00:27:00 - 00:27:55)

Stupidity: Wouldn't it be common sense to have more than one remote to control Robo-Cain? That way, if he destroyed one (and he did), they could still use one to shut him down from a distance (as long as they can dodge the gunfire).

Stupidity: A load of cars is in the tunnel with the overhead lights off, and none of them has thought to put their own lights on (as covered already). Then John gets out of the car, only for one car to suddenly flick its lights on and nearly run him over, having been driving at full speed in the total darkness, apparently.