The greatest catalyst of this episode is that the Doctor and the Dalek are far more similar than he would like to think, both in their capacity for hatred but also humanity. The combatting moralities between Rose and the Doctor come to a head here with striking compassion from our human companion coming out on top. I think it is from here on that we see so much more of Nine embracing himself beyond the darker parts of him forged by the Time War. But regardless, such a solid episode.