Duke Nukem 3D: 20th Anniversary World Tour

An easy way to unlock this achievement is at the beginning of the level ‘Spaceport’ in Episode 2 on the “Piece of Cake” difficulty. When you spawn, enter the cheat code and select the ‘Give All’ cheat. You can turn ‘God Mode’ on as well if you’re so inclined to make it easier.

Before you move, switch your weapon to the Incinerator. Walk down the corridor and turn to the right. You will see a force field door on the left and a pillar in front of you (on higher difficulties, there is a Trooper hiding behind this pillar). Walk around the pillar to the left to reveal a computer console with a Trooper standing in front of it (on higher difficulties there are two Troopers here). As soon as you see the enemy, shoot the Incinerator but immediately pause and save your game (timing is crucial). After it is dead, just reload your save and repeat until the achievement unlocks. This should take about five minutes.

NOTE: You can get this on any enemy in any level but decided on this spot since there was an enemy right at the beginning of the level.