Difficulty: Medium and frustrating.
This is not a hard trophy, it's just frustrating.
Choose a full sized game, such as Conquest with a low amount of players (20ish) and pick a map after studying where to find the RAWR (from the video below). When you gain control of the RAWR hide in a corner nearby and deploy it with R2, while crouching, and use L2 to use it to kill 5 people in a single round.
If you fail then wait for it to respawn and try again.
I managed this on my third attempt on
Propaganda.