Nebula (Marvel Cinematic Universe)

Nebula is the tertiary antagonist in Guardians of the Galaxy, the (former) secondary antagonist-turned-one of the titular protagonists in Guardians of the Galaxy Vol. 2 and one of the deuteragonists in Avengers: Infinity War and Avengers 4.

She is the adopted sister of Gamora and one of the adopted daughters of Thanos.

Nebula is portrayed by Karen Gillan, who portrays Amy Pond in Doctor Who, and Ruby Roundhouse (The avatar of Martha Kaply) from Jumanji: Welcome to the Jungle.

Early life
Nebula was born on the planet Luphom to unnamed parents. However, Thanos killed her parents in front of her and took Nebula. Since her childhood, Nebula was molded into being a weapon and one of Thanos' personal assassins. When she was young, Nebula at first relied upon Gamora, as she was the only one who could give Nebula what she always wanted: a sister when facing Thanos. However, the two sisters were forced to battle one another in training with Thanos watching with glee. Nebula came to resent Gamora, as she was all the family she had left, but Gamora turned away from her. The grudge would last for many years.

Guardians of the Galaxy Vol. 2
Prior to the movie, Nebula attempted to steal Anulax batteries from the Sovereign. However, she was immediately captured and offered to the Guardians of the Galaxy if they destroyed a creature called the Abilisk.

Trivia

 * Nebula's appearance in the movie seems to be based more on her second incarnation from the comics.
 * Despite showing mostly loyal to Thanos the entire time, Nebula in truth despises him for torturing her and using her as a weapon.
 * Nebula and Gamora's relationship in Guardians of the Galaxy was similar to Loki's and Thor's in the Thor films.