10 Amazing Plot Twists In Otherwise Awful Movies
9. Den Of Thieves - Donnie Was The Real Mastermind

OK, maybe it's a little unfair to call Den of Thieves awful, but it was still a pretty forgettable, also-ran heist thriller that dragged on for at least half an hour longer than it needed to. It was only with this excellent plot twist that the film did something remarkable.
Borrowing heavily (perhaps a little too heavily) from Heat, Den of Thieves sees cop Nick O'Brien (Gerard Butler) facing off against a team of robbers led by Ryan Merrimen (Pablo Schreiber). Throughout the film, he forces Ryan's getaway driver Donnie (O'Shea Jackson Jr) to be his informant. Only, Donnie isn't as innocent as he looks.
During the climax, Nick and his colleagues manage to kill Ryan and most of his accomplices, but the stolen money has vanished, and so has Donnie. Shortly after, Nick realizes that Donnie was the mastermind of the heist all along, and that he hired Ryan and his men only to double-cross them and take the loot himself.
This was one hell of a twist that came out of nowhere in the best possible way, retrospectively making the entire film better and more interesting. It's the only truly memorable thing in Den of Thieves, and had the film not ended in such a great manner, it probably wouldn't have gotten its recent sequel, which underperformed at the box office but did better critically than the first film.