The Dark Knight (2008) features six robbers in its opening bank heist.
The sequence begins with masked criminals breaking into a Gotham bank while secretly eliminating one another according to the Joker’s plan. Each participant is assigned a seemingly separate task, such as disabling security, managing hostages, or handling explosives.
The number is six because the crew includes the Joker and five other robbers. The Joker has arranged the operation so that each member believes another will be removed after completing a job, allowing him to keep the stolen money for himself.
A common mix-up is counting only the robbers visible during the first stages of the break-in or treating the Joker as an outside supervisor. He is directly involved in the heist, arriving as one of the masked participants and ultimately being the sole survivor. The opening robbery establishes his strategic intelligence before Batman appears in the story.