Superman and Lois: nobody recognizing Clark as Superman just for dumb glasses (although every Superman media is like that actually)
Flash: when Barry accidentally killed Cisco's brother and change Diggle's child's sex by changing the timeline even though the changes were completely unrelated
Arrow: probably when Felicity didn't ask Oliver for how long he knew he had a son before deciding to get angry at him or not or that Oliver didn't keep the paper with him. I'm not sure what i find dumber
Supergirl: exactly the same as i said with Superman and Lois (although i kinda notice a difference with Supergirl with and without her suit)
Legends of Tomorrow: probably when Jax didn't feel Stein's pain in the 8th episode of season 2 since they're Firestorm
Black Lightning: never watched it
Batwoman: never watched it