You will most likely obtain this in your first match but if not simply try to play it safe by focusing less on pressuring your opponents and being more defensive.
Keep a line of sight on your enemies and always be prepared. Aim for the head whenever possible as it does extra damage. Assists will count as kills so always try to hit enemies even if it is only once. As long as they don't heal for the damage dealt you will get your assist/kill.
This achievement will not unlock until match completion even if you meet what it requires.