Harvey Dent said it best in a line from The Dark Knight that has since become iconic. You either die a hero, or you live long enough to see yourself become the villain. A thought-provoking conversation for Bruce Wayne, but its relevance stretches far beyond just Christian Bale's Caped Crusader.
Movies are full, not only of villains who go through their own redemption arc and wind up as heroes, but also the exact opposite. Heroes who make Harvey Dent's words ring true by breaking bad and taking a complete 180 U-turn on their good guy stance.
While Gotham's District Attorney went through his journey over the course of just one movie thanks to the Joker's input, as have plenty of others, there are those who wait a little a bit longer. Specifically in a sequel, often teased at the end of the movie after initially playing the role of protagonist.
From having their minds manipulated, to reluctantly seeing the benefits of the dark side and eventually showing their true colours, there is no shortage of different ways the good guys have ultimately turned evil.
10. Bucky Barnes - Captain America: The Winter Soldier
The Marvel Cinematic Universe has introduced numerous heroes since Iron Man in 2008, and within that ever-growing roster there have been plenty of dynamic duos. Tony Stark and Rhodey, Rocket and Groot, and Ant-Man and the Wasp, are just a few of these incredible one-two punches.
Then there is Steve Rogers and Bucky Barnes. Best friends back in 1940s Brooklyn, the two were inseparable and were with each other 'til the end of the line, even after one had been captured, had his mind corrupted, and was sent back into the world to kill the other.
As Bucky Barnes in the 107th, the character was a war hero and one of Captain America's greatest allies. As the Winter Soldier however, he was one of the most ruthless and successful assassins the world has ever seen; so elusive and so impeccably skilled in what he did, most of the intelligence community didn't even believe he existed.
The reveal that Bucky was alive in the comics was groundbreaking, as it undid one of the only seemingly permanent deaths in the industry, and when Bucky revealed his face in the Captain America sequel - even though some fans knew it was coming - jaws still hit the floor.