Nebula first appeared in Guardians of The Galaxy and it’s sequel as Gamora’s estranged sister and adoptive daughter of Thanos. She made her detestation be known about her father Thanos for cutting off parts of her body and replacing them with machine. Nebula probably has the strongest distaste for Thanos than anyone else and she finally gets to seek her revenge in Infinity War but I believe it’s a fight she wont make it out of. Her story line came full circle in Guardians of The Galaxy 2. Facing Thanos was the last thing she needed to do I think he will make a statement of how ruthless he is by possibly killing his own daughter.