Start with playing the chapter "Coast" on easy. You dont need to take this achievement on some higher difficulty of course.
When you start this level you will together with your partners talk with a woman with a pig in her hands. Go towards the gate and your girlfreind will go and open it for you.
Go down the road to the beach. Here there are crabs, go around and the first hunter will stand ontop of the big whale. It`s not here you get this achievement, so just shoot him down with your firearm.
Then you need to go back to the lady with the pig, and theres no people there. Go back to the gate and the hunter comes back and start fighting with you.
Make sure you got like half, or more damage done on him before he trows sand in you eyes. Just keep punching him until you get this achievement. It`s possible to miss the achievement easily, so just punch him as fast as you can.