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.
Royal Scam - S1-E5
Stupidity: Agent Sikes arrives at the car park to speak with Spider-Man and parks his car horizontally across two parking spots. A few minutes later, Sikes leaves on the helicopter with Agent Roberts, leaving the car abandoned in the car park. (00:02:06 - 00:04:00)