Here is the full list of all 50 Monster Energy Supercross - there are The Official Videogame achievements.
Create a total of 5 Custom Tracks
Create your first Custom Track
Complete a race without using Rewind in any game mode
Reach Prestige Level 25
Reach Prestige Level 50
Reach Prestige Level 100
Reach the podium in the 250 East Championship in Career mode
Reach the podium in the 250 West Championship in Career mode
Reach the podium in the 450 Championship in Career mode
Pass a Last Chance Qualifier session in any game mode
Win a Main Event at Anaheim 1 in any game mode
Win a Main Event at San Diego in any game mode
Win a Main Event at Anaheim 2 in any game mode
Win a Main Event at Glendale in any game mode
Win a Main Event at Oakland in any game mode
Win a Main Event at Arlington in any game mode
Win a Main Event at Minneapolis in any game mode
Win a Main Event at Atlanta in any game mode
Win a Main Event at Toronto in any game mode
Win a Main Event at Daytona Beach in any game mode
Win a Main Event at Indianapolis in any game mode
Win a Main Event at Detroit in any game mode
Win a Main Event at St. Louis in any game mode
Win a Main Event at Seattle in any game mode
Win a Main Event at Salt Lake City in any game mode
Win a Main Event at East Rutherford in any game mode
Win a Main Event at Las Vegas in any game mode
Complete a race without taking a fall in any game mode
Complete a race with Normal Physics in any game mode
Complete a race without taking a fall or using Rewind in any game mode
Make 50 successive jumps without taking a fall or using Rewind in Time Attack mode
Race a total of 50 miles (80 km) with any bike
Race a total of 150 miles (241 km) with any bike
Race a total of 300 miles (482 km) with any bike
Earn a total of 500,000 SX Credits
Earn a total of 1,500,000 SX Credits
Earn a total of 3,000,000 SX Credits
Win a Main Event in any game mode
Win a total of 25 Main Events in any game mode
Win a total of 50 Main Events in any game mode
Get a Holeshot in any game mode
Get a total of 10 Holeshots in any game mode
Sign a contract with any 450 Sponsor in Career mode
Create your Custom Rider
Make your first purchase in the rider customisation page
Complete a Main Event in a Custom Track created by another player
Complete a total of 10 Main Events in a Custom Track created by other players
Complete a total of 30 Main Events in a Custom Track created by other players
Win a 450 Championship with R. Dungey in Official Mode
Complete any one of the SX Challenges