When you get to the Church during this mission, you'll be attacked by a Bear.
You can either run passed him and continue the missions or fight him.
You get this trophy for fighting the Bear. It can take upto 3 Molotovs and 14 explosive bolts and on Ranger Hardcore it may even take a few normal bolts too.
Loot all corpses in the graveyard before going to the Church gate and then continue on with the fight. Fight hin until you deal enough damage to scare him off. The trophy should pop when the level goes silent again.