Originally Posted by
Jokubas
He first started to grow on me during the Tomb of Sargeras audio drama. I don't remember exactly what it was now, but I believe it was related to how he convinced Gul'dan to remain loyal. For a big demon guy who just wants to destroy things, Kil'jaeden has been given an amazingly... human personality (for lack of a better term). There is a reason and a logic behind what he does and says. That's not easy to pull off with such a relatively basic villain.
As for him turning over a new leaf, I'm still not sure if that will happen with either him or Sargeras. However, a rift between them could still lead to other outcomes. Perhaps Kil'jaeden betrays Sargeras for the sake of victory, only for that victory to end up being the opening the Void needs (and thus a victory that Sargeras would have sacrificed).