The Fantastic four movies and Batman & Robin.
I mostly remember the scene where Peter was dancing down the street, showing how "bad" he turned after being possesed by the symbionte.
If you count Mystery Men then it wins, hands down!
All the Spidermans.
Why?
Tobey McGuire.
Those movies aren't terrible, but I hear what you're saying about Tobey. Nothing about that guy says "super hero" to me. Poor casting IMO.
Among all the super-hero movies, some are really terrible (Superman 4, Batman Forever, Daredevil, Catwoman, do I need to go on ?) but wich one is the worst of all ?
IMO, I would say Batman & Robin : Actors playing like shit, dialogues are dumb, scenario is boring...