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