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