Alright, if the antagonist has sprint, and if you both have full shield, and if he sprints and hits you before you can break his shield you will probably be fucked. But if he's far enough away that you can break his shield either with a grenade or sustained fire before he gets to you, you win. If you armour lock before he can hit you and you pop his shield with it, you win. If you have a goddammed jetpack and fly away, you win. If you put on camo, crouch, and move slowly before he can shower the area you were in with bullets, you can escape. If you have a shotgun, you win. If you have a sword, you might still be fucked seeing as how you can sword cancel with a melee, but you stand a better chance. There are lots of situations you are failing to consider that leave you alive. True, most of them don't involve melee, but if you don't like melee, get into a situation where you don't have to punch.