Armored enemies are much bigger and stronger than regular enemies. Typically the armored enemies will have much stronger weapons which makes them a lot more deadly to fight, especially those with shotguns. If you are going for this, it is best to clear out all other enemies in the area first so you can focus on killing the armored enemy without being shot at. Make sure to roll (Circle), and counter (Triangle) to avoid taking any damage. Don't let too much distance come between you and the enemy as he may decide to use his weapon which will cause you a lot of damage. If this happens just roll and get closer to him to initiate melee combat. The kill must be melee only, you cant use a combo of guns and melee.
Defeat 5 armored enemies with melee only