Kouyoku does need something to hype him up as he is supposed to be Chu’s parallel to Shin. However, none of the new Wei Generals have the buildup necessary to truly hype Kouyoku, I doubt Rokuomi is going to die since he seems to be being built up as Tou’s right hand man and Moubu/Tou/Gohoumei are obviously not going to die anytime soon.
This pretty much just leaves Ranbihaku. While Ranbihaku is a fairly hyped individual that could be feasibly killed off this arc, his death would leave Gohoumei without a single decent dualist subordinate for future confrontations, so I doubt his demise is going to happen this arc.
There is also the fact that Kouyoku is hell bent on confronting Tou above anyone else, so one would think that Kouyoku vs Tou is going to happen over any other Kouyoku matchup but Tou is most certainly not going to die at this point in the story.
Instead of outright killing someone, Kouyoku could earn a feat by dealing Ranbihaku or perhaps even Tou a permanent injury. Something along the lines of taking an eye or a left hand. This would give Kouyoku a respectable feat while not removing any important characters from the story.