Bad ideas that in retrospect are still bad
Sometimes a writer will introduce a new concept that might ruffle fan feathers for a while. Often the backlash will subside with time and sometimes the fanbase will even come around to see it as a positive move, maybe even laugh at their initial overreaction.
But what about the times when you look back at a concept, character, or story from years ago and think "wow I still can't believe they did that!"?
Let me start the topic off with my pick:
Superman rocking a mullet was one of the worst ideas ever. Looking at him drawn with that goofy 90s hair one wondered how DC editorial could possibly screw up a character more. And then the Electric Superman happened. In retrospect Superman's mullet seemed an attractive concept when compared to that nonsense.