This achievement is easily done with 3 AI players on normal (or even family) difficulty. Just select one of the long range characters, like Reaver, and stick to the back as much as possible, shooting your gun at enemies from afar. If any enemies get close, just use dodge to roll as far away as possible. It helps to have as many upgrades as possible for all characters, including yourself.
At the end of the level, choose the right hand side path, as the chicken mini-game is easier than the boss. Getting hit during the chicken mini-game still allows you to get the achievement!
Note: If you unlock the Inner Board and get lucky enough to get the invisibility tile perk, choose this level and stay back. You will not get attacked.