Defeat ten enemies in a row with hand-to-hand combat.

To punch someone, press the square button when close to an enemy. To get this trophy, you have to kill 10 enemies in a row by only using hand-to-hand combat. This isn't that hard, however, the easiest way to get this is in chapter 4 after the grenade tutorial. This means you have to kill the first set of enemies any way you want, then trigger a cutscene. Play on very easy if you struggle with it. Below is a video showing exactly what to do.