Yotsuyu was really disappointing.

If her backstory was slowly revealed while she was still in a position of power it would have eased you into the "tragic villain" thing they were aiming for. Instead they just kind of dumped all of it on you after she became Tsuyu and promptly died like 10 quests later. It was a very hamfisted "oh no I did bad things because I suffered bad things please feel bad for me".
I was also hoping the kind of experiences she went through would make Hien take a deeper look into how his country and society works so there'd never be another Yotsuyu. Instead he just completely forgot everything that happened and life goes on as usual.

Fight was cool though.