Here is the full list of all 50 Sonic & All-Stars Racing Transformed achievements.
Triple-Stunt while transforming into a car or boat
Beat your first Staff Ghost in Time Attack
Do a Reckless Boost
Win any event with a Mod equipped
Detonate the Hot Rod at the very last second
Finish 1st a Grand Prix tournament
Freeze an opponent using Ice from at least 100 meters away
Level-up a character
Absorb a weapon with the Glove and fire it back at your attacker
Go All-Star!
Do a 10 second Drift as Sonic
Do a Level 3 Air-Drift
Finish 0.5 seconds ahead of an opponent in a Race
Do a Boost-Start in each vehicle mode
Finish 1st in a Race without getting hit by weapons
Hit 2 opponents with a single Hot Rod Blast
Evade or Block a homing-weapon 3 times in a Race
Hit an opponent with a weapon while looking backwards
Visit every location in the game
Earn your B Class License
Earn your A Class License
Earn your S Class License
Earn your Star License
Earn your Triple-Star License
Complete a World Tour event on Expert difficulty
Manually select a Random Character for a Matchmaking game
Beat all the Staff Ghosts in Time Attack
Unlock Superstar Showdown in World Tour
Unlock every Character in the game
Get a Podium Finish in every Grand Prix tournament
Unlock Mirror Grand Prix mode
Get a Podium Finish in every Grand Prix tournament on Expert difficulty
Win a Matchmaking game
Complete an event with 4 local friends
Roll Left, Roll Right, Backflip, Forward Flip and land as a car or boat
Complete the Dream Valley Ring Race and pass every Ring as NiGHTS or Reala
Beat 01:11.16 in Time Attack as Vyse in Rogue's Landing
Collect every Star in World Tour
Do 5 overtakes in a single Drift
Get a Perfect Drift score on any Drift Challenge event
Finish a Battle Race without losing any lives
Score 90% accuracy with aimed weapons in an event
Finish in 1st Place in all Grand Prix tournaments at Expert difficulty
Collect 10 Stars in World Tour
Get 10 hits by firing weapons backwards in a single event
Do 10 Stunt Combos in a single event
Get a total of 20 hits with weapons in a Race
Finish 1st in a Grand Prix tournament at Expert difficulty
Finish 1st, 2nd, 3rd and 4th with local friends in a 10 player Race
Hit 1st, 2nd and 3rd place with a Swarm attack