Elex

Pretty self-explanatory and maybe you'll unlock it naturally depending on how brave of an explorer you are, but if you wish to grind it out quickly and early in the game, just go to the Berserker encampment and then to the cliff overlooking the Pit, which is just west of Oran's tavern. Make a save at the edge of the cliff, then simply jump into the Pit, which is a long way down, and die. Press start, then select continue, which will load your most recent save, and repeat. This method should take you less than ten minutes, even factoring in load screens.

You can unlock this right at the very start, as your first achievement

As soon as you gain control of your character for the very first time, look to your left and cross the stream.

Use the button to climb up the rocks in front of you, and prepare to meet your first enemy, the biter, at the top. Follow the combat tutorial to defeat it.

Straight ahead of this spot is a small passageway which ends in a chain link fence. (There's an amulet down here and some other items. Not related to the achievement, but hey). You want to head to the right of this until you reach a cliff edge a few steps away, with a derelict radar building beneath you. Directly to the right of this are a bunch of rocks you can climb and jump up using .

Climb all the way to the top, make a save game, and then jump / run off the edge! You'll splat (along with a tutorial message if you've never taken fall damage before), and your achievement tracker will increase.

Do not Land in the shallow stream as even this small trickle is enough to break your fall!

Pause, reload the save and fall off again.

Each death and reload takes about thirty seconds, making this bizarrely rare achievement a five minute job.