Here is the full list of all 50 MXGP PRO achievements.
Become World Champion in the MXGP class in one of the Career modes
Complete a Grand Prix in Extreme Career mode
Become World Champion in the MX2 class in one of the Career modes
Win a race at Valkenswaard in any game mode
Complete a Custom Championship
Win a race at Villars-sous-Écot in any game mode
Win a race at Assen in any game mode
Win a race at Teutschenthal in any game mode
Obtain a Holeshot after qualifying first in Grand Prix mode
Complete the Tutorial
Beat another player's Ghost time in Time Attack mode
Win a race at WW Motocross Park in any game mode
Start the Replay at the end of a race in any game mode
Win a race using one of the Official Riders in Grand Prix mode
Win a race in Grand Prix mode with Options Weather Conditions set to Rain
Win a race at Ernée in any game mode
Win a race at Frauenfeld in any game mode
Go into Free Cam mode from the pause screen in any game mode
Complete at least one lap using the Helmet Camera in any game mode
Race a total of 150 km (93 miles) with any bike
Meet a Main Sponsor Objective in one of the Career modes
Win a race at Lommel in any game mode
Obtain a total of 15 Holeshots in Grand Prix mode or in one of the Career modes
Win a race at Kegums in any game mode
Win a race at Pietramurata in any game mode
Win a race at Leon in any game mode
Purchase at least 3 components from the same Customisable Bike
Win a race at Neuquen in any game mode
NWin a race at Pangkal Pinang in any game mode
Win a race at Losail International Circuit in any game mode
Win a race at Uddevalla in any game mode
Win a race at Loket in any game mode
Win a race at Agueda in any game mode
Purchase a helmet for your Custom Rider
Achieve first place in a qualifying race in Grand Prix mode
Win a race at Ottobiano in any game mode
Win a race at Orlyonok in any game mode
Successfully perform a total of 100 Scrubs in any game mode
Respond positively to at least 5 opponents in one of the Career modes
Save a Bike Setup for the first time
Complete all the Riding in the wet training sessions
Complete all training sessions
Complete all the Braking training sessions
Complete all the Scrub training sessions
Complete all the Starting training sessions
Complete all the Cornering training sessions
Complete all the In-air control training sessions
Sign a contract with a Technical Sponsor for every component of your Career Bike
Use the Rewind for the first time in any Single player game mode
Take the podium 100 times in Grand Prix mode or in one of the Career modes