Blood Drive

The found this easiest to get with Natalya. Weaken two enemies near each other and then use rage (invisibility) and ram them using a boost.

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.

Easiest Way!

To get this achievement I chose single event.
The Game type; Check point rally.
The map: The Gauntlet (To unlock this map you must complete challenge 1)
Charcter: Natalya

Start the game. As soon as it loads chose Triple Treat as your loadout. As soon as the game starts let them get ahead and then follow them, as you follow them press X to activate your rage and and start sniping with your Rail gun (Weapon you will spawn with). If you mess up restart the event. You may need to maneuver a bit to hit your shots.

destroy 2 vehicles using either superstar or natalya'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