I like Zenos as a villain because his motivation hasn't been done to death. He's not another would-be world ruler, a religious zealot, or seeking revenge for anything. My take on him is that he wants to feel alive, which maybe doesn't make him fitting as an iconic villain because it's too close to a real life psychological disorder, but I feel it makes his character darker and his relationship with the WOL more interesting than that of most antagonists.