Agree. He's a one dimensional character who only finds value in life through fighting/killing difficult opponents. I enjoy him and look forward to his role in the story as it unfolds. Also his voice actor in both ENG and JPN is fantastic.I actually kind of like Zenos, mainly because of how he contrasted with a lot of the other notable Garlean antagonists. A lot of them were driven by their devotion to the Empire whereas Zenos is driven purely by his own desires and basically uses the Empire as a means to carry out his search for a good fight and get stronger.
Certainly not the most complicated character but I appreciate his simplicity and I think he's still entertaining.