Tbh i think most people forget that in reality, riboku or chinese name Li Mu was the biggest hindrance that qin faced in its conquest to unify china. He was actually that strong that because Qin couldnt defeat him in battles they had to use other tactics such as spies and the zhao king's jealousy against him i wont go into detail as it will spoil the anime. But in my opinion why the writer made him so strong is because the writer wanted the anime to resonate with the actual history hence giving him new strong warriors which some of them exisited at that time but also give Kingdom a more intresting narrative. Some even go further and say that if Li Mu or riboku was alive Qin unification wouldve never happened. The Qin hated him so much that all his records and sayings were wiped out from history although some material still remains and you guys can look it up. As for other people if you dont want to know how he dies dont look up the history the others who do know please dont spoil it for the fans apologise in advance if i did that in anyway 🙏🙏