Probably Tyn gets my most despised. From her characterization I don't think she has a single loyalty or value beyond her own well-being. At least Sadeas cared about a unified Alethkar, in his own perverse way. Tyn cared for nothing beyond herself, and she'd gut anyone who stood in her way. That kind of callous behavior repulses me.
Maybe Roshone too? The pain of a son dying is terrible, but to go through that, and intentionally inflict that pain on another for no other reason than vindictive malice is pretty despicable to me.