This Achievement is best done with a group of friends or boosters since no one plays this game online anymore. Just get seven kills on anyone including the same person 7 times without getting killed. Must be ranked. Its probably best to run away and hide after you get the seven kills as you need to finish the match to get the achievement and your friends might accidentally kill you.
If you find this solution to be unhelpful, please tell me why in a comment and I will update it the next time I'm online.