Chain ReactionG 20

To unlock this achievement you simply need to blow up 10 vehicles in 10 seconds. The best place to do this is on the top of the third island in Westdyke. Located on the corner of Lemhist St & Sacramento Ave you will find a motorcycle dealership called Westdyke Motors. Before heading over to the dealership you will need to give Packie a call and have him prepare a bomb for you that you can put in a car (Assuming you have unlocked this perk by getting a 75%+ like rating).

Pick up the bomb where packie drops it off (A nearby alley most likely), attach the bomb to the vehicle, and drive to the dealership. Once there make sure you do not sit on any of the motorcycles as it will call the cops to the location. Inside the dealership you will find 8 motorcycles. Use the vehicle with the bomb and drive into the showroom and push the 8 motorcycles together. Park the car with the bomb next to all the motorcycles making it the 9th vehicle. Run outside and grab one more vehicle to bring into the dealership. This is the last vehicle you will need for the achievement to pop.

Once everything is set up, run outside to get a good vantage point and use your phone to detonate the car bomb. You will find it in Packie's menu on your phone. Wait a few seconds and the chain reaction will start unlocking the achievement.