This effect alters a creature’s emotions. Effects with this trait always have the mental trait as well. Creatures with special training or that have mechanical or artificial intelligence are immune to emotion effects.
Fear
Fear effects evoke the emotion of fear. Effects with this trait always have the mental and emotion traits as well.
Fighter
This indicates abilities from the fighter class.
Mental
A mental effect can alter the target’s mind. It has no effect on an object or a mindless creature.
Source: Player Core pg. 141
Your blow not only wounds creatures but also shatters their confidence. Make a melee Strike. If you hit and deal damage, the target is frightened 1, or frightened 2 on a critical hit.