Here is the full list of all 50 Sonic & All-Stars Racing Transformed achievements.
Level-up a character
Collect 10 Stars in World Tour
Freeze an opponent using Ice from at least 100 meters away
Detonate the Hot Rod at the very last second
Triple-Stunt while transforming into a car or boat
Roll Left, Roll Right, Backflip, Forward Flip and land as a car or boat
Finish 0.5 seconds ahead of an opponent in a Race
Go All-Star!
Win any event with a Mod equipped
Beat your first Staff Ghost in Time Attack
Do a 10 second Drift as Sonic
Do a Level 3 Air-Drift
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
Absorb a weapon with the Glove and fire it back at your attacker
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
Finish 1st a 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
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
Do a Reckless Boost
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
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