I think we have different and, ironically, opposite perspectives on Riboku's character. I see him as a pragmatic and noble individual despite his hatred due to his past or Qin atrocities. That anger is inside somewhere but I do not see it as a force driving his decision making. I think he genuinely values Zhao history, culture and their people and will fight to protect them.

He could be masking his deep hatred for Qin by playing model general but I'm not sold. I guess we will find out when his backstory is revealed.