Here is the full list of all 38 GRID (2019) achievements.
Reach Player Level 99
Win an Event with at least 3 other racers using a loan car
Earn a gold trophy in every Career Event in the Career Tab
Complete every Career Event in the Invitational category
Complete every Career Event in the GT category
Complete every Career Event in the Tuner category
Complete every Career Event in the Stock category
Drive a total distance equal to the circumference of the Earth
Complete every Career Event in the Touring category
Win the 'Showdown: Aurora Motorsport' Career Event
Win a race in a Ravenwest livery with Nathan McKane as your team mate
Win the 'Showdown: Ravenwest' Career Event
Win an Event with a full grid having finished the first round in last place
Win a race by crossing the line backwards
Own at least one car in each class available from launch
Win the 'Showdown: Fernando Alonso' Career Event
Complete every Career Event in the FA Racing category
Reach player level 50
Gain entry to the GRID World Series
Win the 'Showdown: Euro Rand' Career Event
Win the 'Showdown: DisruptR' Career Event
Win the 'Showdown: Vulpini Racing' Career Event
Win the 'Showdown: Hammerhead' Career Event
Finish a race with at least 3 other racers without taking any damage
Customise your first livery
Beat your first Nemesis
Beat your first Career Rival
Win your first Career Event
Purchase your first car