I think Riboku is a great man because:
1. his king never support him and consider him a nuisance, but he still become a minister and a great general.
2. many people in Zhao (including many high ranking people) loves him but that is as many as people who want to stab him in the back.
3. His job is 3 times harder than any Qin general because he must deal with: annoying king, corrupt official, and outside threat. Note: Qin general just need to deal with outside threat (or war) because Ei Sei will deal with any internal problem, and Riboku dont have this luxury (eh he is the one who deal with inside problem because he is a minister too).
4. Without him Zhao will fall far sooner.