6. Batman and Robin
Oh, where to begin with Batman and Robin? It's probably the most notorious superhero movie ever made, simply because of the devastation it caused the Batman franchise. A sequel to 1995's Batman Forever, it was a critical disaster (that also underperformed at the box office) because of how it completely misunderstood its title characters and set comic book movies back decades.
With Bat-nipples, one-liners, neon lights, and ice puns aplenty, it's hard to believe this movie exists in the same series of films as Tim Burton's revolutionary 1989 franchise-starter Batman. It's even more jaw-dropping that it comes just two films after Burton's own twisted masterpiece Batman Returns, because it's just so far removed from what those beloved outings were.
George Clooney's performance as the Caped Crusader was one of the many gripes fans had with the movie, but the overall unseriousness of the script was really to blame for Batman and Robin's failings. The film that was produced as a result of that was like a larger-than-life pantomime that was anything but the modern Batman; and that's why it brought about an unfortunate end to the original Batman series of movies.
As a lifelong Batman fan, I completely understand why so many people still consider this such a disaster. It killed the Batman movies and that is not easy to overlook. That being said, the movie itself definitely falls into the "so bad it's good" category, and out of context, on its own, and without judgement, Batman and Robin is kind of a good time. It's a bizarre, over-the-top, and cringe-inducing good time, but the campy spectacle is hilarious fun; and honestly, it's about time that we appreciate it for that.