Here is the full list of all 45 The Fall of the Dungeon Guardians achievements.
Reach the End of the Game
Reach Level 20
Complete the Treasure Hunt
Kill 1000 enemies
Double check any loose end that may save your life
Reach Level 19
"Now, look at these boots, and tell me they're not Legendary !"
Reach Level 18
Reach Level 17
Do 150 damage in one hit
Reach Level 16
Reach Level 15
Spent 15 talent points in the same Specialization Tree
Spent 7 talent points in 2 Specialization Trees
Reach Level 14
Reach Level 13
Reach Level 12
Reach Level 11
Do 100'000 total damage
Do 100 damage in one hit
Reach Level 10
Reach Level 9
Walk 10'000 tiles
Reach Level 8
Reach Level 7
Reach Level 6
Pass through a fake wall
Reach Level 5
Go all the way in & out of the Fireball room without being touched by any fireball
Reach Level 4
Run away from an enemy during a fight
Never flee for a whole level (after level 1)
Reach Level 3
Kill a boss or an elite with only 1 party member left alive with less than 5% of their HP left
Kill a Boss without using Active Pause
Do 50 damage in one hit
Do 10'000 total damage
Kill 100 enemies
Kill an Elite without using Active Pause
Reach Level 2
Walk 1000 tiles
Kill 10 enemies
Kill your 1st enemy
Walk 100 tiles
Do 1 million total damage