MAG

A Bunker Buster Ribbon is earned when you blow up 2 bunkers in one round. You'll need to get it 3 times to get the trophy. An easy way to earn these ribbons is to play as a Platoon Leader, and use the Precision Strike on a bunker when the anti-air is down. Considering this attack can be used every 5 minutes, playing in Domination will give you all the time you need to get this ribbon easily.

For further information: see Ribbon guide (#5).