Here is the full list of all 19 Unfinished Battle achievements.
Level 2 Unlocked
Level 3 Unlocked
Level 4 Unlocked
Level 5 Unlocked
Level 6 Unlocked
Level 7 Unlocked
Level 8 Unlocked
Level 9 Unlocked
Level 10 Unlocked
Level 11 Unlocked
Level 12 Unlocked
Level 13 Unlocked
Level 14 Unlocked
Level 15 Unlocked
Level 16 Unlocked
Level 17 Unlocked
Level 18 Unlocked
Level 19 Unlocked
Level 20 Unlocked