These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Moral Event Horizon: Flying Fox killed Kai's mother, then had her stuffed, mounted and put on display. Years later, he shows Kai his handiwork.
Player Punch: Sort of. The scene in which Flying Fox, after spending a portion of the game gleefully tormenting Kai, captures her and then proceeds to hang her by the neck from a really big height (apparently killing her in the process), deliberately doing it as Nariko watches is just plain upsetting. Nariko's anguished screams at Kai's apparent death really serve to make the moment hit even harder (but don't worry, Kai gets better).
Tear Jerker: The ending. Also, the moment in which Bohan is lying, helpless and blinded, while Roach runs to his aid, telling him that he's going to take care of him and begging Nariko to "please let me take him home" qualifies.