Easy way we found to do this with you and two teammates. ("You" refers to the one boosting for this achievement, "teammates" are the two helping the booster.)
Build hounds for speed. Yours should be equipped with Piles (the spiky sticks), as many as you can load up. Teammates should have very light weaponry (e.g., the lightest, cheapest machine guns available).
Now go in a war zone against the CPU. The teammates' job is to lure the CPU hounds away from the base, and to keep the enemy from firing on you. They can do this by running around them or hitting them with their light weapons. (CPU hounds generally will turn and fire at whoever is firing on them.) It is critically important that the teammates DO NOT destroy any hounds.
Your job is to sneak around behind the base and hit it with the piles. When you are one or two shots away from destroying the base (it may take a round or two of experimentation to figure out how many shots it takes to destroy a base with your piles, so you know which shot is "the last shot"), stop firing and signal your teammates.
Teammates should then die -- either by letting themselves be destroyed by CPU hounds, or by holding the BACK button to abandon the hound.
When you have confirmation that both teammates have blown up, *then* finish off the enemy base with the last one (or two) pile shots.
You will win the match being outnumbered 3:1. Do this nine more times (total of 10 unlocks the achievement).
Note that some CPU squads will attempt to stay and defend their base. We had much success, in these cases, having the teammates push through them and actually lure the CPU squad further *behind* the base, and having the booster drive right into the front of the base and destroy it from there.