the thing about Chuck Bass is that he likes the challenge associated with Blair, but he only likes it when it doesn't interfere with his perception of her as his mirror image. her personhood and occasional desire for autonomy is something that makes him deeply uncomfortable at best, and violently angry and vindictive at worst. he initially only sees her as an extension of Nate, writing her off as his best friend's hot, if prudish and anal retentive, girlfriend. he never acknowledges her as a human being outside of that archetype until he eventually graduates into seeing her as a sexual being instead. he's known her since they were both children, and she still has to contort herself into somebody that's palatable to his tastes before he begins to think of her as somebody worth looking at. before this shift, it was Serena that he was fixated on in this manner, and it would've remained that way, had she not disappointed him by coming back from boarding school Boring. ultimately, it boils down to the fact that his interest in women doesn't extend to their individual identities. instead, he wants a warm body that he can trigger into sexy disputes at his discretion, a Thing that he can pour his negative emotions into through sexual predation or verbal put-downs. he doesn't want a person. and Blair tries to be that for him, more often than not. but unfortunately for the both of them, Blair Waldorf is more human than anybody could possibly fathom.