beat a player who is in the middle of a 20 or more win streak.
any easy way to do this is to set up a vs match (offline) with one round win. sign in a second player and kill the profile you want the achievements on 20 times. after this, go to your main profile and kill the second player.
If you have done the right you will get a message saying you have got a gold star.
after that go online and play a match to get the gold star