I once had a villain who was actually a PC from a previous campaign. He was a tiefling who had been shunned by society first in cheliax, because tieflings are seen as a singn of weakness for their parents (a really cool piece of fluff in my eyes btw) and then in most other countries for the more obvius reasons.
The whole ordeal made him hate the concept of fate, wich lead to a "I have to become the most powerful so no one can decide my life." Once he had left behind most mortals, he realized that the gods still ruled his fate and that of everyone else.
So he went on and tried to create an atrificial starstone to simply make EVERYBODY into gods to even the playing field.
Since he figured that once he was a god, he could just fix everything he had broken, he followed this goal with ZERO caution or restraint.
Sadly the campaign never progressed to the point where the PCs would have been confronted with his reasoning.