This is a combat related trophy and it can be done either in Campaign Mode or Versus Mode. For the trophy, you must simply kill 5 enemies with Blood Frenzy in a single Campaign Mode mission or a multiplayer match. A blood frenzy is when either a player or and Spec Ops Solider is sustained too much damage and lost a large amount of blood. This will trigger blood frenzy as the player or Spec Ops Soldier is now bleeding and cannot stop it. This will cause the surrounding zombies in the area to catch the scent of the blood and will get excited and hungry as they attack you or either the Spec ops Soldier who's bleeding.