First of all, this achievement requires at least 2 controllers as there is no online play.
You will want to set it up as follows:
Multiplayer > Collect > Hunter Hunt > Durability Set to 100
This will make sure you can kill your opponent quicker.
With your first controller drive over to the other car, line your truck with theirs and press
to shoot, this will hit the other car and cause it damage.
The further away you are, the more damage it causes and would be quicker for you, so if you're able to line up further away and shoot to hit the other truck then do it.
It is actually possible to one shot them on 100 health if you are far enough away.
If you run out of ammo, you can collect more scattered around the map.