Worms

Since the damage is cumulative, the object is to deal 500 points of damage to your opponent's worms. If you play a single player match, it will be 4-on-4 worms with each worm having 100 points in a 3 round match (each round being complete after all of one player's worms being dead).

Given this information, if you kill all 4 worms in the first round and 1 more in the next, you'll get this achievement. However, you would have to be the one dealing every last point of damage for you to get this achievement by only killing 5 worms total. It does NOT count if they hurt themselves, you hurt yourself, or if you knock them into the water (as that is instant death, not points of damage).

If you play single player, you should be able to get this achievement by the end of round 2.