This is the best way ive found to get the onyx Veteran Medal its time consuming but worth it if you want it.

Basicaly all you need to do is just do a setup as the same as "Party like its 1999" Achievement, But if you dont know how to do that heres the tut.

Setup a Warzone private match,
Number of rounds and rounds to win - 1
Number of bots - Fill
Bot difficulty - Any

And Leave the rest as it is.

Now This wil work better if you have a wired controller or a controller that will never turn off as you are not going to be moving unless you want yor "MVP" ribbon which gets you superstar cole.

basically it will take up to 6 hours for 500 matches so its better to do around 6 hours a day But thats just my opinion

So far i have unlocked superstar cole with GOLD MVP medal and have a SILVER Veteran medal:D

Hope This has helped

-No thanks and rep is needed but appreciated thanks