There are massive SPOILERS for Avengers: Infinity War below, so read ahead at your own risk.
In the comics, Nebula ends up enduring a lot more torture, which ends up turning her into a zombie-like character.
The storyline involves Thanos joining the Avengers to get to the Infinity Gauntlet and place it and the Stones in their rightful places.
Karen Gillan has teased that her Nebula character has a pretty large part to play in Avengers 4, which makes sense since she barely had any screen time in Avengers 3.