Army of TWO The Devils Cartel

The only other standing solution for this achievement outlines a method for getting it that can only be accomplished having purchased some special edition of the game new, which contains a redeemable code. If you purchased the digital version/got the game on Games with Gold or bought the game used, obviously a $7 DLC is of absolutely no use to you for one achievement.

In the mission Rally Point, chapter 7, you'll spawn in the middle of an ambush and surrounded by vehicles. As you deal with the enemies, there are 15 vehicles along this road that you can blow up toward this achievement. Once Amp and Bravo decide to leave this stretch of road, you can continue on for another stretch of road that contains 17 more cars for you to explode. Take note, however, that the Bautista dump trucks are invincible and cannot be blown up, so don't waste your ammo. Your only checkpoint in this mission is in the alleys between these two stretches of road, so you must decide whether to reload the checkpoint at the stairs or continue to the second half of the mission to grind there.

Using the AMR-50 sniper with explosive rounds, you can set any vehicle on fire with three shots, and the M1 assault rifle with explosive rounds requires 15 shots. These were my selections for guns that fit my play style the best, so your ammunition mileage may vary depending on which guns you choose.

Self Explanatory: Blow up 50 cars over the course of the game.

If you don't get this during your playthrough, a great spot for car destruction is the first Overkillers contract, on the mission Rally Point. You start in Overkill in front of a large parking lot. Blow up the cars (which will happen very quickly in Overkill), and continue through the level, blowing up the many cars on the streets. Do this once or twice to reach your 50.

You know... I'm surprised that nobody uses this as a solution but if you select the mission "Outside Contract" , "Suicide Run" chapter, you'll have the option to either drive the truck, or shoot using the turret. Use the turret and shoot as many cars as you can. You should get it no later than your third attempt of trying depending on how many cars you've destroyed during the campaign. If you don't pull it off by the end of the chapter, restart the checkpoint. The achievement will unlock after you've destroyed your 50th vehicle.

Just thought I would add in that Helicopters count towards this achievement, just unlocked for me when I was on the Confrontation (Burning Bridges) chapter.