For this achievement, you have to get 100% followers in the 4 provinces in the Narco Road DLC.
Warning: Some are reporting that this achievement is glitching on them. Unfortunately I don’t have any extra tips as the requirements are already extremely linear. The more people what report this to Ubisoft the more seriously a patch will be taken. As of writing I don’t think this happens to everyone.
You Must do the following in each area:
1) Complete all Main Missions.
2) Complete all Green Side Missions (Animal traffic, Amphetatruck, Airspray and Lost Cars)
(Video attached for Lost Car locations).
3) Complete all Electro Challenges (Drifts, Climbs, Aerobatics, Bike, Jump).
You should get 3500 followers (the max in a region) after completing the very last item of the list above. The missions, side missions and challenges provide you with EXACTLY the max amount of followers. There is no extras, you must complete all the above for all the followers.
Although straightforward, it will take a while. After doing the story and a bits and bobs it still took me 90mins-120mins per region, so it will take you 6-8 hours in total even after the story to complete this unless you are a significant pro at this game and never die or fail a side mission.