Gamora

Gamora is the deuteragonist of Guardians of the Galaxy and Guardians of the Galaxy Vol. 2 and a character in Avengers: Infinity War.

She is the adoptive daughter of Thanos, adoptive sister of Nebula, Proxima Midnight, Corvus Glaive, Cull Obsidian and Ebony Maw and love interest of Peter Quill.

History
Gamora was born in late 1979 to an unnamed pair of Zehoberei parents and lived with them peacefully on her homeworld. She had a father who didn't stress diplomacy; however, there is nothing said about her mother [1]. As a child, her adoptive father Thanos killed her parents and their people in front of Gamora. However, Thanos spared Gamora and kept her as his adoptive daughter But also turned her into a weapon.

Thanos
Adoptive Father and Former Master. Gamora hates him for turning her into a weapon and no longer considers him her father when she became a Guardian of the Galaxy

Nebula
Adoptive Sister and former rival. As children, they were forced to fight one another in battle, causing Nebula to hate her sister (but the two of them had a better relationship other than the rest of their other siblings. (Main article: Nebula and Gamora).

Peter Quill
Love interest. Gamora has been friends with Quill for over three years and has a romantic attraction to him. However, she is still unsure of her feelings for him until the very end of Guardians of the Galaxy Vol. 2, an "unspoken thing" as both of them put it, as Gamora is willing to enter a romantic relationship with Peter.This is proven true in the last film, where they are in a romantic relationship (Main article: Star-Lord and Gamora)

Role in Avengers: Infinity War
Years later, the Guardians responded to a distress call from the Asgardian ship the Statesman, only to discover the remains of the ship and its passengers. After recovering Thor Odinson, Gamora was enamored by Thor's physique. Thor recounted his encounter with Thanos, guessing that Thanos was heading to Knowhere to find the Reality Stone and noting that no one knew of the Soul Stone's whereabouts, much to Gamora's displeasure. At this, Quill, Gamora, Drax, and Mantis chose to go to Knowhere while Thor, Rocket, and Groot travelled to Nidavellir to forge a new weapon to stop Thanos.

En route, Gamora made Quill promise to kill her if she ever got captured by Thanos, admitting that she knew a secret that Thanos did not. When they arrived on Knowhere, they discovered Thanos interrogating the Collector on the Reality Stone's whereabouts. Gamora then ambushed Thanos and managed to kill him, only to discover that it was all just an illusion and that Thanos did have the Reality Stone. Thanos then incapacitated Drax and Mantis before holding Gamora hostage and thwarting Quill's attempts to kill her.

Taking Gamora to his ship, Thanos revealed that he knew she had lied to him on the Soul Stone's whereabouts. He took her to a captured Nebula and used the Power Stone to torture Nebula. This was enough to force Gamora into admitting the Soul Stone was on Vormir. He then took Gamora to Vormir, where they encountered the Red Skull, the Soul Stone's guardian. The Red Skull explained that to obtain the Soul Stone, one must sacrifice someone they love dearly. Gamora scoffed at this claim, believing Thanos was incapable of loving anyone but himself, only for Thanos to reveal that he loved her and tearfully sacrifice her by hurling her to her death

Avengers: Endgame
The 2014 version of Gamora appears in the film, where she joins Nebula and the other Avengers and Guardians of the Galaxy in defeating Thanos.