Make sure you have unlocked some golden weapons as they make this achievement much easier and faster to complete.

Start the level Chimputee Battle Master as that is one of the easiest and shortest levels of the game. I choose Normal difficulty.

I went with four golden Laser Guns and two Golden Shotguns. I don't recommend the Rocket Launcher because of the splash damage. Also, the Grenade Launcher just sucks so don't use it.

Finish the level by killing the boss. With these weapons it should take about 20 seconds. It is not even necessary to collect the big health boost above the starting point.

The important thing to remember is that this achievement will work even if you quickload during the level. So if you get injured, load the last save and try again. Watch out for the enemies spawning around the boss.

SAVE OFTEN - when there are no enemies around you, hit that quicksave button.

This is actually one of the easiest achievements of the game once you have some golden guns.