Werewolf: The Apocalypse - Earthblood

During the intro mission of the game, when you have learnt the stealth parts, you are then able to start attacking people. As soon as you can do this, there are two groups of enemies, one directly in front of you and one a bit behind it. Walk to the bigger of the groups and do a heavy attack with triangle. You should easily hit 5 in one go, if not you can restart the checkpoint or simply do the same anytime within the first mission as they clump up alot here.

Simply attack a group and this should unlock pretty easily.