My main picks:
Catwoman
Red
The Losers
Steel
Tank Girl
Barb Wire
X-Men Origins:Wolverine
Hulk
Superman III
Superman IV
Batman&Robin
Captain America
Fantastic Four (1994)
They all had potential, they were all worthwhile projects. They just weren't executed well.
Now, if you have seen the Justice League TV movie...anyone could tell you such a thing is never, ever going to work. A live-action Justice League TV show which is half Power Rangers, half Friends. Staggering that anybody thought for a second that was a good idea.
I've seen a lot of bad comic book movies which I think still have some right to exist for whatever reason. But The Spirit was just wrong.
Supergirl (Of course imo the character should not have been created in the first place.)
I don't think that GhostRider should have been made. It's a stupid character and it made for a stupid, terrible film.