5. Captain America (1990)
Captain America wasn't as well known as some of his Marvel counterparts when he headlined his first MCU movie in 2012, but previous attempts were made to introduce him to a more mainstream audience. One of those was the infamous 1990 movie and, well, it's easy to see why it hasn't been well-remembered.
While the film had a limited theatrical release internationally, it was direct-to-video in the US. Unfortunately, looks exactly like a direct-to-video movie should (and nothing like a Captain America movie should). The suit wasn't very good (can you believe this was released a year after Batman?) and the fake rubber ears on each side of the cowl were ridiculous. Sure, superhero movies weren't taken all that seriously back then, but again, Batman was changing the game; this was setting it back.
The basic outline of a Captain America movie is there. If you watch the trailer, you'll recognize many of the plot points from both his comic book and MCU origin stories. But that's it; it's just a sequence of familiar Cap moments without so much as a coherent story to tie it all together. And unfortunately, that makes it impossible to extract any kind of nuance from it.
In the film's defense, it does fall into the "so bad, it's good" category on occasion, but it's not enjoyable enough to make itself at home there.