>>100275966He killed her and then brought her back as a half-dead half-alive zombie and the reason he did it was because Nebula claimed he was her biological Grandfather.
That pissed him off because he's a nihilist who loves Death and him creating life is something that he views as an affront to Lady Death.
Also Nebula isn't his daughter in the comics and the only person Thanos truly considers his kid is Gamora. Mainly because he chose her to be his daughter and actually raised her and there's feelings involved.
Thanos only really cares about Death, Gamora, and Adam Warlock and to a certain extend his father Mentor, his brother Starfox and Mar-Vell. Everyone else he doesn't give much thought about.
