Stupidity: Spoiler alert. After the son makes it out, he could get a rescue team to get his dad by going in where he came out.
Stupidity: Kale screams for Ronnie after he sees the image of the club girl on the videotape, and Ronnie proceeds to just stand there and doesn't even bother to go up to Kale to see what is wrong. Had Ronnie gone up the stairs to Kale, then there was a likely chance that they could escape from Turner easily.
Stupidity: At the start of the tanker chase Sanchez shoots at Bond. He manages to get in the cab and throw the driver out, who lands on Sanchez's car. Sanchez then gets in front of Bond and has the ideal opportunity to just shoot the cab up with his machine gun knowing Bond is driving, but he doesn't.
Stupidity: Quinn wasn't able to kill Dr. Sullivan, so decided to kill herself to save her sister (by dying earlier and ending the curse). Instead of telling her younger (teenaged) sister about the Narcan and how to use it, she writes Narcan on her upper arm, assuming her sister will see it in time, know that there is a syringe in her pocket, and not hesitate to inject the Narcan. Quinn left too many steps up to chance and did not take the necessary precautions to help insure she could be revived. At the same time, a registered nurse - even a recent graduate - should know that this would not be the circumstances under which Narcan might be successful in counteracting the morphine. Taking time to say, "I love you, Jordan. I'll always be with you" was wasted time that should have been used giving her sister instructions because Quinn (erroneously) believed her plan would work. (01:17:08)
Stupidity: After Roy escaped from the factory, he encountered a metal garage-door-type gate that was open at the bottom to the height of his knees. Trying to sneak away and in obvious pain from his injuries, it would have been quicker, quieter, and probably less painful if he crawled through the opening. Instead, Roy pulled downward on the chains, making a lot of noise, and it didn't even get the gate halfway up before he bent over to get out. The gate went up more after he stopped pulling on the chain. (01:15:29)
Stupidity: To quietly kill the hotel valet he is replacing, Diabolik throws a knife at him from distance, hits him in the back, and then drags his body in the middle of the street to the nearest manhole, leaving a long streak of blood he does not conceal. If this sounds pretty risky and unsafe especially for a meticulously planned murder, you have also to consider that in the comic book from 1963 this movie otherwise faithfully adapts, Diabolik did nothing this foolish; he quietly killed the guy strangling him next to the spot he'd dump his body into.
Stupidity: Noah chases one suspect while Leslie chases the other two. Noah eventually pulls out his gun and says, "Stop, police!" Leslie doesn't even try to draw her weapon until she hears sounds from the nearby brushes - but she barely has her hand on the holster when she turns around and gets punched in the face. Leslie is knocked over and the other man she was chasing repeatedly hits her in the face, quite hard. Her injuries could have been avoided simply by having her gun ready to aim and use. (01:04:48)
Stupidity: After Jack's attempt to send a distress email to his colleague fails because his office computer has been hacked, he secretly attaches the camera pen to Janet to move unmonitored. If he wasn't willing to cooperate, why doesn't he just secretly write a distress message on a piece of paper and show it to a colleague?
Stupidity: Rick tries to kill Frank at his boathouse by dumping gasoline all over the place and using Ray Coleman's lighter that Frank had. At this point, Rick has gasoline over his arm, but instead of properly cleaning it, he opens the lighter immediately and has his arm burned. Surely a criminal genius like Rick wouldn't have risked this as this is a loose end. Further mention goes to when he has the bathroom door open for no reason while medicating the burn mark, which enables his wife to see him and discover who he really is.
Stupidity: When Jonathan is chasing the truck to try and save Sarah, he could have removed his heavy backpack and run faster...but instead just leaves it on. No wonder he wasn't fast enough.
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: The team raids the house and locates 5 people inside deemed to be Russian operatives. They are subdued and placed on their knees, while some of the team works on gathering intel from the home. The subjects should have been handcuffed/zip-tied. Since they were not they were able to grab stashed weapons and cause a gun fight which led to one of the entry team's members being killed and all the Russian operatives killed. It's common knowledge to restrain people. Cops and military always restrain. (00:04:00 - 00:12:00)
