Gamer has been removed
Start a new game on easy and equp yourself with the Lucky Bastard perk. You must be in combat to use it, so head down to the 98th floor. Once you're engaged in combat, click the perk (in the upper left hand corner of the screen, beside your health and food bars). You will one-shot the monster.
Note: You only unlock perks after you have beat the game at least once!