Here is the full list of all 35 Shredders achievements.
Complete 10 gaps
Call the snowmobile 50 times
Unlock all the gear in the game
Complete The Lawn Darts Mission
Collect 10 collectibles
Complete the AirBorne Mission
Complete the Cliff Drop Mission
Complete the Canyon Jump Mission
Complete The Village Roof Run Mission
Jump over the Rugby pole at the park
Rock the invitational!
Complete the We Own The Sky Mission
Get a Score of over 6666 in a single trick
Complete the Spin Dizzy Mission
Spin a total of 360.000
Transfer 3 rails
Complete The Dammed Mission
Complete the Hit The Streets Mission
Complete the Factory Worker Mission
Complete the Forest Cross Mission
Jump 1000 times
Bail 100 times
Complete The Beat The Street Mission
Collect all the SHRED letters in a mission
Ride 10 km of deep snow
Land a 1080
Ride 50 km
Land a double backflip
Complete the Fast As Hell Mission
Land a 540 Indy
Complete 25 gaps
Collect 40 collectibles
Call the snowmobile 500 times
Ride 10 km with the snowmobile
Play in a private session