10 Superheroes Who Broke Bad

One of the most famous superhero falls from grace is Jean Grey's transformation into Dark Phoenix, even though it technically wasn't Jean Grey who did it.

While returning from a mission in space, the X-Men's shuttle was damaged. Jean sacrificed herself to pilot the ship back to Earth, even though it meant absorbing a fatal amount of radiation. However, she then emerged from the shuttle as the Phoenix, empowered by a cosmic force that had been moved by her sacrifice.

For a while, Jean used her greatly boosted psychic powers to be a huge asset to the X-Men, but then the illusion-casting Mastermind used his powers to make Jean believe she was the Black Queen of the Hellfire Club and the X-Men's enemy.

Jean broke free of Mastermind's powers, but the process drove her insane. Accessing her full powers, she turned into the Dark Phoenix and flew off into space. She then made a star go supernova, wiping out an entire planet.

After regaining her senses, Jean was consumed with guilt over what she had done and allowed the Shi'ar to execute her.

Except, surprise, turns out that wasn't Jean at all. It was later retconned that the Phoenix Force had placed the real Jean in a cocoon to heal her from the radiation poisoning and taken her form, deluding itself into thinking it was her. This allowed Jean to rejoin the X-Men without all that pesky genocide business hanging over her head.