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 all 42 challenges
Unlock every driver
Play with every Chief
Complete 100 races across any game mode
Beat 15 ghosts in Time Trial mode
Play with 10 different chiefs
Perform 500 drifts across any game mode
Finish 10 Arena games
Activate 100 Chief skills
Unlock 10 crew members
Perform 25 jump boosts in a single race
Perform 25 Slime stunts in a single race
Buy 5 different kart parts in the shop
Finish every race of a single cup with at least 10 Slime Tokens
Hit opponents 30 times with projectiles
Discover 5 different shortcuts
Unlock a chief for the first time
Collect 500 Slime Tokens in total
Begin a race with a boost
Unlock a driver for the first time
Get the first place in a cup
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