see attached file--- there is a Chenarus Deathmatch, for arma 2, which uses addRating in the init and is persistent after respawn when you play against another real person in the DM.
then there is the Agia Marina Stratis Deathmatch...that one is for arma3, obviously, and is an exact re-creation of the deathmatch. play with another player in MP, and you'll see that your first kill is positive, but your second is negative. the rating is only making them an enemy until after they die.