Here is the full list of all 13 Fighties achievements.
Unlock all items
Unlock all characters
Beat arcade mode on hard
Get past level 20 in survival
Get past level 10 in survival
Beat arcade mode on normal
Unlock a character by playing the crane game
Beat arcade mode on easy
Get past level 50 in survival
Complete survival mode
Unlock all costumes
Complete main menu background
Beat arcade mode on hard with all characters