Nebula

Nebula is one of the main characters in the Marvel Cinematic Universe, debuting in Guardians of the Galaxy. She is one of the daughters of Thanos and the adopted sister of Nebula. Like Gamora, Nebula was abducted by Thanos and trained to be an assassination Eventually, Nebula became a member of the Guardians of the Galaxy and became a full time member after everyone who was victim of the snap was resurrected

Pre-Series
When Nebula was a little girl, she was taken from her parents and trained to be an assassin of Thanos. While She wanted the love of her sister, Nebula realized that Gamora would always beat her at everything and wouldn't realize this until her audlthood.