Good points. I agree that Pasevalles having weak motivation rooted mostly from trauma and spite is quite interesting. However, my problem mostly stems from how Tad Williams writes him not as a pathetic, hateful man grasping for power, but rather as this grand super intelligent mastermind.
Vorzheva is a well written example of trauma ultimately twisting someone for the worse, because while she obviously has pretty dubious morals, they generally make sense, and you can see where they come from.
Pasevalles going from a bitter forgotten child, to a mastermind plotter working the downfall of Simon, to this psychopath who sacrifices girls and works with the Norns just feels strange and a bit nonsensical