The Koenigsegg Regera is unlocked for purchase after completing the story. Buy the "Race" version at the Race dealership, not the Drag version. Winning Drag races with the Drag version does not unlock the achievement. The Regera costs 794,205 credits. You can farm credits by replaying events and selling cars and performance upgrades you no longer need. Opening shipments is also a quick way to get credits. Play the "Midnight Run" race. It is in the Desert area in the middle of the map, and the shortest race in the game. It only takes one minute to complete. You must place first in the race without hitting any other cars, guard rails, walls, rocks, etc. to get the "1500 bhp... Easy" achievement. You are allowed to hit street signs since they do not damage your car. If you hit something other than street signs, restart the race to try again. It may take a few tries. Most importantly, try passing all opponents at the first bend in the road. The trickiest part is not hitting any opponents as they tend to drive recklessly. The sooner you take the lead, the better. You still need to drive fast though. Otherwise, your opponents will catch up to you and potentially crash into you from behind. Just practice the race a few times to get the hang of it.