Valerian Mengsk: Another good character IMO. His early mission appearence aside, I'm glad he took the path he did. Good lines, good interaction.
Arcturus Mengsk: A common complaint about Mengsk in WoL was that he was ineffectual. I kind of agree(d), but didn't see it as something bad, but rather as character development. In a position of power, power for his own sake, loses his edge, etc. The problem with that theory is that he definately has that edge back in HotS, both in regards to his psychological attacks against Kerrigan (e.g. Raynor) and Korhal. He's outmanauvered, but it shows him being pro-active in his responses to her. And he's far more ruthless, such as the way he callously destroys the
Moros. I guess if I had to reconcile the two, it would be that the 'best' of Mengsk comes out when he's challenged, such as when leading the SoK, or dealing with Kerrigan. Either way, Mengsk was a badass here, and I thought he was handled excellently.