"
so perfect I've
Never been quite so fucking deep in
It goes on
I think that this means that she sucks in bed, honestly I think this part of the song is supposed to be humorous, because whenever I hear I start grinning and laughing at this, it's like a major burn to me. But by saying "Now she's so perfect I've never been quite so f--king deep in" means that when they had sh-t that she never let him go all the way in, and by killing her, he can finally go as deep as he cans.