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