As the achievements states, you must play in battle commander. You unlock all Battle Commander game modes at level 7, and these gamemodes are the same as the normal gamemodes (there are TDM, Ground Control and Skirmish varients). These are alike in everyway to their non-Battle Commander counterparts, except that in the game, the AI marks those who play really well as threats. Consequently as your threat level increases, the AI will try harder and harder to get people to kill you. Fun isn't it. Getting to a 5 star threat rating is hard, very hard, nearly impossible as the only way to do so is to get over 15 kills without dieing either on foot, or in a vehicle while the AI labels your general location on the map for enemies to see and places a larger and larger bounty on your head. However the RQ-10 Parrot makes things much easier. Because it cannot attack the game treats it a different way, in order to increase your threat level all you have to do is mark enemies and you have to do so 45 times without being shot out of the sky, or having your vunerable body killed by an enemy.
To make this achievement much easier, create a custom class, that has perks which improve drones. By level 7 you will have access to 3 and can equip all at once, one increases your drone's speed, one increases its max health, and one increases battery life, also remember to equip the RQ-10 Parrot to one of the reward spots. Nothing says idiot, like taking all the perks but forgetting the drone itself.
The RQ-10 parrot costs only 250 BP in game. When you start the game, you start with 500 BP, and you know all the enemies are on the other side of the map, so clearly this is the best time to go for the achievement.
Move back into a discreet area, go prone and call in your RQ-10 Parrot. My advice is to fly up very high; enemies look ahead, not up. Swoop down when you see anyone, mark them, and then regain altitude. You can remark an enemy when the red mark indicater begins to flash, which starts happening about 4 seconds after you mark them. The great thing is that, while enemies are notified that they've been marked the warning itself isn't very noticable, and given that so many people snipe in this game, it's very easy to simply float above them and just keep marking them as they will be concentrating on scanning for enemies, instead of paying attention to the warning.. (One time I had 4 snipers on the same rooftop, This was after I had gotton the achievement, but you still get 20 BP with every mark, so I was making 80 BP every 3-4 seconds, good times, I even hovered over one sniper and just hovered up and down to add insult to injury (Note: RQ-10 Parrot teabagging is not recommended when going for this achievement))
In order to get the 3 star threat achievement, you must mark 25 enemies in a row. In order to get the 5 start threat achievement, you must mark 45 enemies in a row (some solutions above are saying it's 30 and 50 but they are wrong, I even watched the video in the above solution, they got points for 5 marks, and then they get to a 1 star threat, and then every 10 marks after that their threat level increases). Also every time your threat level increases, your health and batteries are restored to full making this only easier. So after what should be at most only a few games of trying, you will have yourself a nice 105 GS.