Thanks to Karen Gillan's amazing performance in the Guardians of the Galaxy and Avengers films, the world knows who Nebula is in the MCU. Like most of the characters in the films, some changes were made so they could be more easily introduced and made accessible. Nebula is one such character, seeing as her appearance, characterization, and interactions with others in the comics differ greatly from what we've seen on the silver screen.
Gillan may be an amazing Nebula, but she isn't much like the one we've seen in the pages of Marvel Comics. Because of this, there are a lot of misconceptions about who Nebula is, what sort of villain she might be, and how she's impacted the various attempts to take over Marvel Comics' cosmic universe. Here are the various aspects of Nebula from the comics most folks may not know.
Nebula first appears in the comics aboard a spacecraft with Captain Marvel, but it isn't the same one seen in the MCU. Carol Danvers's identity as Captain Marvel is relatively new in the books; instead, Nebula meets Monica Rambeau, the second person in Marvel Comics to take on the heroic mantle.
While pretending to have lost her powers, Rambeau meets Nebula, who immediately blasts her with a laser blast. Captain Marvel turns herself into light, making the strike completely innocuous. She ends up joining Nebula's crew to get home, but the pair continue to have a contentious relationship.
Throughout her time in the comics, Nebula has claimed to be kin to a large number of people, but no evidence has ever been offered. She claims to be Thanos's granddaughter, but she hails from the planet Luphom, not Titan. She also claims to be the daughter of Zorr, one of the few remaining members of her species.
There hasn't been any information over the years concerning her mother, so it is possible that some of what she claims is true.
While Nebula claims to be Thanos's granddaughter in the comics, she is absolutely, without a doubt, not Gamora's sister. That's a big difference from the films because the relationship between Gamora and her adopted sister Nebula is one of the most important aspects of both characters.
In the books, the two not only aren't related, but they've also had little to no contact for most of their history. For decades, they don't even know of each other's existence. It's not until the crossover event Annihilation: Ronan that the two cinematic sisters finally meet. They join up for a time during the event but then go their separate ways.
In the MCU, Gamora is introduced as the adopted daughter of Thanos, but there hasn't been a lot of detail concerning who she really is or from where she comes. Fortunately, the comics have a lot more information. If you thought she was a Kree due to her blue skin, you would be wrong because she comes from a planet called Luphom, which makes her a member of the Luphomoid race.
There's no way anyone in the Marvel Universe will ever have a chance to visit Luphom thanks to Galactus, the World Devourer. He found the planet and consumed it, which means he killed every living creature on the planet. The only Luphomoids left in the Marvel Universe were those who were off-planet at the time of Galactus' consumption.