There are numerous places throughout the story campaign where you will be forced to fight hand-to-hand with several normal enemies, topped off by a fight with a large "brute" enemy.
All you need to do is defeat the brute without taking any damage from him. I found the best strategy is to wait for him to attack and execute the button prompt that appears to counter-attack him. After the counter-attack, he will be momentarily stunned so hit him with 2 or 3 regular melee attacks, then wait to counter him again. If you go too crazy on attacking him, you will miss the counter-attack and take damage.
If you do take damage, you can always just restart the checkpoint and try again.
Note: The trophy will unlock as soon as you defeat a brute enemy without taking damage.