Blood Drive

Reggie's rage is the best to use as it does a lot of damage.

You can start a match with full rage (which gives you three rage attacks ready to be used) which will help and also use the radar to see if there are enemies grouped together.

It might also be an idea to try it on Capture the Skull missions as enemies usually follow each other closely. I got it when a group of enemies were bundled together against a wall trying to get the skull.

Reggie's Surgical Strike has a timedelay, so for me it was much
easier to use Kelley's Gravity Well Rage to get this achievement.

Just play Capture the Skull on Flightmare and choose the Triple Threat loadout for 3 rage attacks.

Get rid of the minelayer and search for the sawblades, railgun, minigun or whatever you like.

Weaken your enemies with your weapon of choice until their health is really low.
Then drive nearby and shoot 2 of them up into the sky with the Gravity Well Rage.

If their health was low enough, they'll be wrecked when they touch the ground again.

I actually found this the easiest of all the "Wreck 2 vehicles" type of achievements. The problem for all of these achievements was to get 2 cars close enough together and with low enough health to wreck them. Since Reggie has such a powerful Rage ability you don't have to worry about softening cars up first, just getting them together is the issue.

To achieve that I started a checkpoint race on Helter Smelter and picked the Pimped loadout (full boost and full rage are what you need for this method). As soon as the race starts boost towards the first checkpoint, once there press X and carry on till the second checkpoint, use rage again, after that one go to the third checkpoint and use your final rage. You have 3 tries this way, if you don't get it just restart. The reason I found it much easier this way is because of the checkpoints you KNOW where they are headed. So it's only a matter of getting there ahead of them, activating your Rage ability and hoping they arrive right as it fires (for those unaware of his rage ability, it's basically a giant laser beam that fires a few seconds after you activate it). I got a triple kill on the first checkpoint using this method, sometimes the AI mess each other up though so it may take a few attempts.

destroy 2 vehicles using either reggie or kelley's rage ability in a single go, best way is to activate the rage ability while near a large group of other vehicles and then shoot everything you have at them