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