Here is the full list of all 35 GRIP achievements worth 1,000 gamerscore. It takes around 50-60 hours to unlock all of the achievements on Xbox One.
Destroyed 50 opponents
Destroyed 5 players without dying
Destroyed 4 players without dying
Pulled a wheelie on the ceiling
Finished the tutorial
Made a hit with a round of Raptor bullets
Finished a carkour course
Won by passing the leader in the last second
Performed a double-somersault when airborne
Made a hit with a Scorpion while airborne
Raced 50 laps in total
You hit 3 or more cars with a single Hydra
Finished 1st 3 races in a row
Finished 1st in a race
Finished a 20 lap race
Created a custom tournament
Destroyed 3 players without dying
You destroyed 2 players without dying
Finished an arena match
Destroyed an opponent
You hit an airborne opponent with a Scorpion
Destroyed some scenery
Finished a race
Went from 10th to 1st within one lap
Race 250 laps in total
Race 1000 laps in total
Finish 1st 6 races in a row
Average a speed 700kmph+ in a race
Hit 3 opponents with a charged RamRaider
Hit Mach 1 in a race
Destroy 100 opponents
Destroy 250 opponents
Finish all carkour courses
Finish the campaign
Hit only cars with salvo of Hydra missiles