Bollywood Thriller
He transitioned from "oh, he's just being Kanye" to being an outright jerk in this moment.
It should be noted that quality of music also went downhill after this.

Personally, I don't blame Kim. I do think Amber fed into his ego though. Further edit...not blaming any female for his behaviour, but I think his pre-Amber girlfriend kept his ass in line more and didn't encourage his douchiness as much. Everyone since seems to want to ride on his coattails/notoriety. At times, everyone's ego needs to be reigned in.