Here is the full list of all 33 MX Nitro achievements.
Buy all bikes.
Get and equip Enforcer set.
Perform Superman 50 times.
Win a race with a half-wheel lead.
Win a ranked race.
Crash 300 times.
Drive 1000 seconds on rear wheel.
Made a flashy finish.
Overtake a total of 100 riders.
Get level 3.
Buy and equip a new customization item.
Spent a total of 5 minutes in midair.
Complete the First Tournament.
Take First place in any race.
Rode to finish without crashing.
Complete 50 challenges.
Perform only Fresh tricks in Freestyle and win.
Collect all stars in Online Race.
Finish a race with 108 seconds time.
Perform all 4-button tricks in the game at least once.
Speed up to 180 km/h on Drag.
Get 5000 Trick Score in one combo.
Fly 200 meters in one crashflight.
Found his Doom.
Collect all Track Quest's marks.
Earn a total of 50000 credits on Slums races.
Get full Nitro Tank 100 times on Desert tracks.
Hoard 500 000 credits.
Beat Pedrolino.
Beat Punk Lizard.
Beat Steelhead.