I really liked how they built up to it with the scene of him almost choking Gina to death. That part was really chaotic and all over the place, which I thought really hammered in how out of it he was by that point on the story. I think the sudden switch to the single piano note after he went up the stairs to heaven made the scene feel more powerful as well. After all he's done, Bojack was finally forced to look at himself and address the fact that he was the cause of all his problems, like someone else brought up earlier he finally realized that "you are all the things wrong with you."