
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: Characters repeatedly make note of how hard to kill the Wraith are, but sometimes, especially in the final episode(s) of season 1, they go down easily in a few bullets each, and then don't even regenerate as the characters turn their attentions elsewhere.

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.

The Killer - S1-E1
Stupidity: To make the hit, The Killer places a bomb on the ceiling of his room - which is the floor of the victim's. He has absolutely no way to know where in the room the man will stand and when we see the explosion, it does not even touch the couch. The brilliant plan of the flawless killer is anything but brilliant or flawless.

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: There's no way April would mistake Slash, his debut episode in Season 4, for one of the turtles as he's got spikes on his back, dressed differently too.

Storm Before the Calm: Part II - S1-E38
Stupidity: Shane could have easily avoided the blast from Lothor by simply flying away to dodge it. Instead, he just hovers over him and allows his Battlizer to be destroyed.

Claudia and the Secret Passage - S1-E8
Stupidity: The fact that Kristy found the ring that was missing for 40 years just sitting on a windowsill in the secret passage makes no sense; Dawn and Claudia were just by that window earlier in the episode in broad daylight.
Suggested correction: We don't actually see where Kristy found the ring; it was dark, and the girls were chaotic.

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.

Recognition - S1-E17
Stupidity: After fighting Wootox in Sky's body, why didn't Cruger contact the other Rangers and inform them about the body switch? This would have spared everyone a lot of trouble.

Stupidity: Hungarian Police Lieutenant Benedeke Erdös has broken right arm in a cast. Although his arm is in a cast, he is still in uniform and carrying his firearm in a holster on his right side. There's no way he can draw the weapon or secure it. (00:20:45 - 00:21:19)

Zorro's Ride Into Terror - S1-E8
Stupidity: When Diego sees that the passage door is opened, he invites Sergeant Garcia to sleep in his bed. However, Diego never tries to close it, and during the rest of the scene, nobody (even Captain Monasterio) seems to see it open.

Is Lupin Burning... ?! - S1-E1
Stupidity: Despite the fact that there are 100 (literally) cameras around the racing circuit and (again literally) everyone from the staff to the fellow racers works for the Scorpion gang, Jigen and Lupin's switch can happen without anyone noticing, even if it involved racing side by side for a lengthy period of time.