To unlock this achievement you must lead 6 of today's best scores while in 8 player freeburn (not in a challenge or event).
Important: The achievement will NOT unlock if you lead in 7 or 8, it has to be 6.
The 'today's best scores' consist of
Air Time
Barrel Rolls
Drift
Flat Spins
Jump Distance
Near Miss
Oncoming
Power Parking
When I achieved this on the Xbox One version I did so by hosting my own game, setting good scores with a drift car for drift, barrel rolls, parking, flatspin etc. then I did challenges until 8 players were present then eventually got it. I was at 9 ahead when 8 players were present and had to wait for others to knock it down to 6. When I hit 6 the achievement unlocked.
This is certainly the most frustrating achievement of all due to luck, skilled players and quitters. A boosting session would make this much easier to achieve.
If you have any related questions or I can help leave a comment or send me a message.