Here is the full list of all 19 Scott Pilgrim vs the World: The Game - there are Complete Edition achievements worth 1,000 gamerscore.
Defeat Matthew Patel without losing a life.
Defeat the Twins simultaneously.
Defeat an enemy by throwing an object at him while he’s already down.
Play through a World and reach the boss without getting hit.
Clear the game once with Scott.
In a multiplayer game, reanimate another player at least 25 times.
Eat every food items
Defeat 1000 enemies.
Clear the game in single player on the “Supreme Master” difficulty setting.
Buy all the items of a shop during the same visit.
Defeat at least 200 enemies using interactive objects.
Unlock and call all strikers.
Catch a flying object at least 25 times with Knives.
Clear the game in 90 minutes or less with Knives.
Perform at least 10 consecutive head stomps successfully with Knives.
Complete your first online match.
Play Online with all characters at least once (including Wallace Wells).
Clear the game once with Wallace Wells.
Knockout 200 enemies in online mode.