Not sure how many times you see those annoying enemies but if you only kill them with the QTE consisting of the circle button from beginning to the end of the game you should have the trophy. Also if you happen to miss the trophy after beating the game simply farm them in the arena.
there's a handful of times that you have the chance to get this trophy however i HIGHLY recommend that you get it out of the way the very first encounter you have with keres wraith. it will be way easier to kill 2 leave one and die and rinse and repeat till you have it done. cause later in the game you have multiple enemies alongside the wraiths that would make dying and redoing any section over again a pain in the butt.