This will require you to have completed the majority of the gold level races. Once you have reached the required points, the 'Horizon Final' event will be available. The race is just like any other festival event where you race against 8 cars, one of them being Darius. Although you are required to complete 5 laps, the circuit isn't all that long or difficult. If you find yourself struggling to win, be sure to race on easy difficulty and turn on all assists. Once you win the race, the achievement will unlock.