Robin

Note: Please do not add "Joel Schumacher died in June 2020" reason, because this was before that happened. Robin was a spin-off film to Batman and Robin, but was cancelled due to the critical and box office failure of the film.

Plot
The plot is for the most part unknown. It would likely focus on how Robin became Batman's sidekick.

Why It Was Cancelled

 * 1) Batman and Robin flopped at the box office and received extremely negative reception from critics, audiences and fans of Batman (mentioned earlier).
 * 2) Joel Schumacher admitted that both the spin-off and other planned films in the franchise should have been the studio's next step instead of producing Batman and Robin.

Result

 * Robin was permanently cancelled.