Here is the full list of all 27 Nickelodeon Kart Racers 2: Grand Prix achievements.
Unlock all crew members
Hit opponents 500 times with items
Complete 100 races across any game mode
Play with every Chief
Complete all 42 challenges
Beat 15 ghosts in Time Trial mode
Finish 10 Arena games
Perform 25 Slime stunts in a single race
Perform 25 jump boosts in a single race
Unlock every driver
Finish every race of a single cup with at least 10 Slime Tokens
Activate 100 Chief skills
Play with 10 different chiefs
Buy 5 different kart parts in the shop
Unlock 10 crew members
Discover 5 different shortcuts
Perform 500 drifts across any game mode
Collect 500 Slime Tokens in total
Begin a race with a boost
Hit opponents 30 times with projectiles
Get the first place in a cup
Unlock a driver for the first time
Unlock a chief for the first time
Destroy a projectile with any item or Chief skill
Complete your first race
Get 3 stars on every cup in all game speeds
Buy every item in the shop