In the MCU, Gamora's origin is pretty straightforward. As Guardians of the Galaxy reveals, Gamora's planet was wiped out by Thanos, who rescued her and raised her to be a warrior. She turned on Thanos, teamed up with Star-Lord, Rocket, Drax, and Groot — and the rest is history.
Simple, right? Just wait. In the comics, Gamora first appeared in Strange Tales #180, but we don't learn her history until Warlock #10. As the story goes, Thanos correctly predicted that the villainous Magus, a time-warped version of hero Adam Warlock and leader of the tyrannical Universal Church of Truth, threatened his plans for galactic domination. So, Thanos needed a weapon he could use to stop Magus before he grew too powerful. He found one — in the future.
Years after Warlock #10 takes place, Magus' soldiers killed Gamora's kinsfolk, the pacifist Zen Whoberis, as part of their crusade. Thanos, however, managed to rescue Gamora at the last minute, took her to the present, and trained her to stop Magus once and for all. Her assassination attempt fails (although she manages to kill the people responsible for the yet-to-occur Whoberis genocide, preventing it from taking place), but helps Adam Warlock beat Magus and the Church anyway.
The saga doesn't have a happy ending, though. In the current timeline, a hostile alien race, the Badoon, wiped out the Zen Whoberis anyway, while Gamora flat-out dies when she turns on Thanos. But more on that shortly...
