All the way to the point where neither of them really has the heart to cut off the other's worst instincts... Which, of course, leads straight to how Zero ends.
Giving Saber a partner who knew what she could do and was willing to step back and let her do it, while backing her up properly from the sidelines, was so very refreshing.
Ahhhh, Nepkat. It's... an interesting ship, that one. In many ways Nepeta's just what Karkat needs, someone patient, caring, willing to listen and able to sift the important things out of his rants without getting annoyed by it.
And Nep needs someone to help her find some direction lest she just roll around being a wild catgirl at everything, so having somebody so determined to do shit, even if it's not necessarily the best idea, is really good for her.
If Hussie had, you know, actually ever intended to take her seriously, that could have been a very supportive and reliable relationship between the two of them, romantic or not.