User blog comment:Zathronas/Analysis by an author - My analysis of volume 3/@comment-10390252-20160215132025

I think that Cinder explained her motivations very well in Beginning of the End: "I want to be powerful, I want to be strong, I want to be feared." There will probably be some bad or pitiful explanation behind it but what she is is a very weak and very timid personality who, as these personalities sometimes do, has chosen to confront her weakness and fear by making everyone else scared of her.

Her gloating monologue to Pyrrha more-or-less confirmed this. She was completely incapable imaginging that Pyrrha had a motive for confronting her other than the possession of power as an end in itself. The idea of possessing power for a greater cause is likely unimaginable to her because, to her, self-deification is the highest aspiration.

What she wanted was to be powerful so that she'd never have to be afraid again. Then Ruby's wellspring opened up and Cinder learned the ultimate truth for those who wish to hide behind power as a protection: That there is always a bigger fish.