When filmmakers say a movie is based on true events, they’re trying to give the movie a stamp of legitimacy. For the most part, moviegoers understand that they’re going to see a story based on an actual event and not a documentary, and they’re willing to allow some creative leeway.

Even so, audiences know when a movie grossly exploits what really happened, especially when the event involves the dark side of humanity.

To determine the worst movies based on real events, 24/7 Tempo developed an index based on several metrics from the Internet Movie Database and Rotten Tomatoes. The index is a composite of the movies’ IMDb rating, the Rotten Tomatoes audience score, and the Rotten Tomatoes Tomatometer score.

Many films on the list explore immoral actions as well as tragedies. Some of these films deal with subjects such as murder and homicide. Others are haunting tales based on alleged incidents.

All of these failed real-event processing aren’t sinister. Biopics are a Hollywood staple, but many fail to find favor with audiences and critics, despite prominent actors in the lead roles and award-winning directors behind the scenes.

Some bad movies, of course, achieve a kind of iconic, ironic “so bad, it’s good” status. People look at them just to poke fun at them or bask in their deficiencies. These are the 25 absolute worst movies of all time.

Click here to see the 50 worst movies based on true events

To determine the worst movies based on real events, 24/7 Tempo developed an index based on several metrics from the Internet Movie Database and Rotten Tomatoes. The index is a composite of the movies’ IMDb rating, the Rotten Tomatoes audience score, and the Rotten Tomatoes Tomatometer score. All ratings were weighted equally. Only films with at least 20,000 reviews on IMDb and 2,500 ratings reviews on Rotten Tomatoes were considered. Additional data on domestic box office and production budgets per film comes from industry data site The Numbers.