Yeah, honestly, Seymour's motive doesn't make much sense and changes too often to feel like a real plan. The game makes it obvious from the beginning he's meant to be a hate sink and the only thing he cares about is power.

Caius gets points for sticking to his woobie characterization, but he suffers from Bleach syndrome in terms of being so horribly overpowered and strategically invincible that he lacks any catharsis factor as a villain. That's not to say every villain needs this catharsis factor, but XIII-2 is a Shaggy Dog story and makes it infuriating to watch because of it and its largely because Caius ultimately achieves everything and his powers make it impossible for him not to. LR tries to make it more of a pyrrhic victory for the player, but even then I felt like he gets off way too easily. Its the problem of making a villain too sympathetic, especially for a soft-hearted developer like SE that doesn't like going dark very often.