Here is the full list of all 20 Asphalt 9: Legends achievements.
Unlock 30 cars
Complete 40 Seasons in Career mode
Obtain 800 Career Flags
Star Up 30 cars
Reach Reputation Level 10
Perform 100 Upgrades
Drift 75,000 meters
Upgrade Garage to Level 5
Perform 50 Traffic Knockdowns
Destroy 600 race objects
Perform 240 seconds of Air Time
Win 25 Races in Career mode
Perform 50 Barrel Rolls
Perform 15 Perfect Nitros
Perform 25 360s
Perform 10 Knockdowns
Perform 15 Nitro Shockwaves
Complete 1st Season in Career mode
Win the 1st race
Perform 5 Perfect Runs