The laggy player is easier to kill in long distance : your reticule is bigger than the foes, so you have more chance to touch him considering you don't know his real position. The guy charges on you with the sprint bouton. Cause of his connection, he becames absolutely untouchable, but you can still manage to hit him with some bullets at this distance for the reasons I said in my last paragraph. Problem : the few bullets you manage to get, do less damage to him (than most of players) cause to his double armor. And then he manages to enter in a close combat with you and then he is sure of winning cause to his laggy connection. Also, the SCAR has a high rate of fire, in consequence he can kill you rapidely, even if he hasn't got any improved damage upgrade, and don't let you any chance to damage him.
You have more chance to kill a laggy player when he run, than in close combat. But with double armor he manages easier to enter ALIFE in close combat ! It's pretty impossible to kill a laggy player in close range (you are doomed to die at the moment he get close to you).And you can have all the speed you want, cause your laggy target is running, it will not help you so much. If you want to kill a laggy player, you have to keep your distances with him.