Here is the full list of all 42 Gear.Club Unlimited 2 - there are Ultimate Edition achievements.
Drop out of a race
Buy a category B car
Own 5 cars
Beat Payton Hills
Build the Wind Tunnel
Complete 25 solo races
Change the color of one of your cars at least once
Install 5 parts on your car
Earn your first Million Credits
Build the Tire Workshop
Join or create a Club
Buy a category A car
Beat Ken Cole
Build the Mechanic Workshop
Buy a category C car
Buy a category D car
Build the Body Workshop
Put back a part of lesser quality
Install 10 items in your Performance Shop
Change the look of your Performance Shop
Put 5 stickers on the same car
Add a body part to one of your cars at least once
Change the rims of one of your cars at least once
Beat Vassily Rykov
Beat Teruko Nakamura
Beat Primo Biondi
Beat Gustav Reuter
Win Payton Hills' car
Win Vassily Rykov's car
Win Teruko Nakamura's car
Win Primo Biondi's car
Buy Gustav Reuter's “Koenigsegg Agera RS Custom”
Complete 25 races with no collisions
Own 15 cars
Own 30 cars
Visit another player's Performance Shop
Win the Porsche 911 Type 930
Win the Ford GT40
Win an Endurance Championship
Complete an endurance race without changing your tires
Finish a race on less than 2% fuel
Reach 400 km/h on the Le Mans circuit