Stupidity: Donna runs in to save everyone from the collapsing pylon, dying in the process, despite the fact that Superboy or Raven, both more powerful/resilient, could have stopped it falling without any issues whatsoever. Not even like anyone was distracted - the fight was over, they were all just standing around.
Stupidity: The super powerful Romulan commandos (no doubt with the help from the higher-ups infiltrated in the Federation) managed to touch up the footage of the fight in the roof so to remove every trace of the Romulan agents present. But Picard has been running, dodging blasts, ducking, and is knocked back by a huge explosion caught on camera and not deleted; we see it in this episode and it is unequivocally not caused by him. What is the point of going through subtly deleting every trace of the aggressors when it is transparent that something real happened and it's not all Picard's imagination? And the police simply take Picard back home from San Francisco to France without questioning him, not caring about investigating the explosion in the heart of the city involving a famous Admiral battling invisible enemies. If the conspiracy can erase anyone from the tape, why not erase Picard too, or the explosion and explain how he ended up K.O.'d differently?
Stupidity: When the new principal is addressing the student body, Avalanche tries to impress Kitty by causing a couple of small earthquakes, one of which causes the scoreboard to crash to the floor below. The principal laughs off the incident and continues to address everyone instead of either evacuating the area or having everyone take cover.
Stupidity: One of Rogue's defining character traits is her inability to have physical contact with another person because of her powers and the sorrow it causes her. Several episodes of this show, however, featured devices that could suppress mutant powers, the inhibitor collars being the most prominent. Despite this technology at their disposal, they never even think to have Rogue wear an inhibitor device for times she would like to touch someone. Even if she didn't want to wear those specific collars, a character like Beast or Forge could easily create a new and harmless device by reverse engineering and adapting the existing ones. This of course would eliminate Rogue's ongoing dilemma and potentially curb her development as a character, but it doesn't make sense from the standpoint that she longs for physical contact with others.
Stupidity: When the bad guys are discussing the plans inside a private jet, the scene finishes and there's a shot of the plane in the sky. The plane immediately veers to the right, and spins almost 90°, as fighter jets do when they turn quickly. If there were three people inside, (one of whom was in the bathroom) they would have been thrown about the cabin quite violently. (00:11:25)
Stupidity: Whilst Reva is running across the rooftops, there is a moment where she does a backflip in order to propel her forwards towards the next rooftop. If she was attempting to jump between roofs, then doing a backflip would not have been useful as it would only slow down her momentum instead of build it. (00:25:28)
The Revenge of Robin Hood - S1-E16
Stupidity: The Time Tunnel technicians send a homing beacon to the dungeon to help Tony and Doug, but through the episode nobody notices the well-lit, futuristic-looking object propped against the dungeon wall next to the door.
What If... The Watcher Broke His Oath? - S1-E9
Stupidity: Ultron says he can destroy galaxies with a thought. So regardless of Dr. Strange's protection spells, he could destroy the planet they're all standing on, or evaporate the atmosphere, leaving them all suffocating in space, and just step away from the fight entirely while they die.
Stupidity: During a raid of a Latin stash house, Hailey and Kim find two girls with a pistol. In Spanish, they say no bullets. Kim interprets what the girls say and Hailey replies, l didn't know you spoke Spanish. Makes no sense that a partner on an elite police unit in Chicago would not know a member of the team speaks Spanish. (00:14:58)
A Bad Reflection on You - S1-E38
Stupidity: The decision to risk revealing their identities to Bulk and Skull is one that the Rangers could have easily avoided. Since they tell the bullies to cover their eyes and ears, under the false pretense of a magic trick, they could have simply teleported to the Command Center, or any other secure location, and then morphed, well away from prying eyes.
Worlds Apart - S1-E2
Stupidity: The bad guy kills the deputy in the swamp, then later sees a little girl who witnesses the killing run away. He then searches the boat for a weapon and runs off after her after he finds a machete, without even considering the officer's gun still in its holster. Abby proceeds to make the exact same mistake later when she finds the dead officer (meaning there's danger nearby) and hears the girl screaming and runs in the direction of the screaming without taking the gun to protect herself.
Stupidity: Andor and Luthen set a vehicle to drive and distract the security team. The vehicle is destroyed, and they immediately round the corner in full view of the team on a speeder and drive away, then blow up the vehicle. They could have driven away on any number of other streets without revealing that they weren't in the vehicle, keeping their escape secret. And if they blew it up before the team looked too closely they might have even been deemed to have been killed in the crash.
The Perks of Not Being a Wallflower - S1-E3
Stupidity: Superman finally smashes the weirdly strong bad guy through a wall, then goes to Lois, says "he's gone", and whisks Sarah to hospital. But he has no idea if the bad guy is "gone" or not - they've just had an epic fight, he has some sort of super strength / resilience, and for all Superman knows he'll come around in 10 seconds and finish the job of murdering Lois.
Stupidity: While flying over the jungle in the Dragonfly, Dr. Quest uses the Dragonfly's speakers to tell the Po-Ho tribe he is their Air God and is angry for the tribe taking hostages. While he was at it, Quest should have ordered the Po-Ho's to release the hostages.
The Night of the Firebrand - S3-E2
Stupidity: West is introduced to, then knocked unconscious by Vixen as she hides a club behind her back. A trained Secret Service agent like West would not have let his guard down in this situation, as the entire fort was awash in bad guys.
Stupidity: In the original, the knight of the Phoenix suddenly appeared during the arena fights interrupting the show and stealing the Gold Cloth. In this remake of the saga, Sienna/Saori Kido leaves the arena by plane during a bombardment that occurs way before Nero/Ikki arrives to steal the Cloth. There is no reason why she would fly off in her VTOL without bringing the Golden Cloth with her, then (there's a lot of time for that). Instead she leaves it for the 4 Saints for them to "protect it", against a whole army and on foot in the middle of the desert.
Stupidity: The inspector knows that his house has been bugged; he does not know how many bugs and cameras are there, he just knows there are some. He does find a bunch of them with great ease when he gets back home - making you wonder how could he have ignored them to begin with, since all it takes is for him to raise his eyes, they are fairly big black cameras who do not camouflage at all for the most part. He then proceeds to make a phone call to the big baddie from his landline. Nobody in their right mind would do such a thing. Heck, you wouldn't want to use your home phone for such a call even if you didn't know that someone just put bugs all over your house.
Stupidity: The last remaining Xindi, in desperation, attempts to release the virus over the fan, despite the virus not being fully ready. However, it seems the only reason he didn't release the virus at that time was he had to seek cover from Archer and T'Pol shooting at him and to start shooting back at them. However, he had plenty of cover from the rooftop stairwell, which was right next to the fan, and he had enough time to dump out the contents over the fan.