Romance
Mr Glass seemingly tries to seduce Ruby, but also subsequently retrains her for sedation and ultimately tries to trick her into going on a Death ride.
I was a bit puzzled my Glass's motivation throughout the movie:
Is he trying to seduce Ruby to sleep with him, because Mrs. Glass is a druggie and not satisfying him physically?
Is he trying to seduce Ruby to seemingly have an affair with him, only to betray her and compound the charges against her? He types her a report, after all, and gets her caught Plagiarizing.
Why does Glass kill the parents? For the money for his cars? It would seem that a person of his social standing should be able to borrow money through better means than loansharks, though.
The Glass antagonistic was left largely underdeveloped as a character.