Luca Blight actually has a very good reason for being batshit insane.
He and his family were literally just taking a stroll when they were all ambushed by bandits. Instead of protecting his wife and son, Agares literally saved his own hide and left them to the bandits mercy. As a result, his wife is sexually assaulted by the bandits (giving birth to Jillia) while Luca is forced to watch. All of this while he was still a child.
If I were forced to watch my mother being r***d while my dickbag of a father left us to their mercy, and THEN after making sure HE was safe, send in someone to retrieve us, I'd have serious issues as well growing up.
Totally agree. Sad that they didn't explain that a bit better in the game though. Luca's better than any of the Squenix baddies to me.