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