A nice touch when Harry is fighting the troll: When he engages his killer instinct, from then on the troll is only referred to as the "enemy", in one case even with a capital E.

Interestingly, while Harry explicitly mentions "censors off" (concerning no more screening off of potential killing methods), that mode of thinking also engages other filters, dehumanizing (de-troll-izing) the creature he's fighting and only seeing it as "the Enemy".