Early on during the Tour, you will be in Patagonia. The last event in this region, is called the "Fitz Roy" and they recommend you use a wingsuit for the event, because of the large gaps.
Choose this event, and make sure you are NOT wearing any wingsuit. You should have a very low survival probability (4%).
Just take your time down the hill, making sure to land tricks and build boost on small jumps. On large jumps you must boost and hold "A" (to ready your rider) prior to the jump to clear any gaps. All gaps have ramps marked with skulls, meaning these need high speeds, with preloaded jumps. Also, you are allowed 3 total rewinds, if you ever take a nasty spill, and they will not prevent you from attaining the achievement.