G'day
Attel Malagate was an alien, with unfathomable motivations.
Kokor Hekkus was either an alien or mad, or both. But Thamber was a construct of which any gamer would have to approve.
Viole Falushe was mad (erotomanic: which is pathetic even though it is creepy).
Howard Alan Treesong had the most complicated and amusing schemes. But I found that his multiple personalities made him less than fathomable as a character.
But Lens Larque was human and sane, and his ambitions were utterly fathomable in light of his background and circumstances. And his plotted revenge on those sanctimonious racist snobs the Methlen was utterly delicious!
So I think it has to be Lens Larque.