This is an unmissable story-related-ish trophy that you will gain near the end of Chapter 1 "Flight to the ford" whilst you are playing as Aragorn in the forest being accompanied by hobbits. If you somehow magically don't gain it here, you'll fight LOTS more throughout the game, so it's all good.
*** Spoiler - click to reveal ***After Frodo has been poisoned by the black riders, you will need to get to the other end of the forest whilst collecting plants boost the timer up, when you eventually get to the end you'll come across a female alongside a horse, just after speaking to her, a troll will come up behind you, so simply defeat him for the trophy to pop. Try your best to evade his attacks as he's a hard hitter, and don't get too cocky with your hits, there will be points you have to use an icon strike to do bonus damage, so use these to your advantage