Transformers: Revenge of the Fallen

The best way to get this achievement is to play the East Coast Downtown Mission: Down With History. The only objective is to destroy the Museum and in the process you will be faced with an infinite flow of autobot opponents, so just forget about the Museum until the very end and just go after the autobots. The achievement doesn't pop up until the mission results so you might want to keep replaying it over and over until you get it. Also, I believe your kills are invalid if you don't medal so don't mess around for too long.

Replay the Deception Mission 'The Guns of Cairo'.

- Play as Long Haul
- Use your Primary weapon (bombs) to take out the 2 autobots that attack you (You will never have more than 2 at once)
- Use your flamethrower to take out the Axiom Gun's energy bar low
- Fire all time bonuses for extra 10 seconds each.

You need a bronze medal within 12 minutes for it to count so at 11:30 destroy the Axiom Gun. Using this method you will kill 70-80 autobots easy.