Here is the full list of all 46 Deep Dungeons of Doom achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Buy all Mercenary skills
Buy all Crusader skills
Buy all Witch skills
Find 10 secrets
Causing more than 100 points of damage in one hit
Buy a level 6 skill with the Crusader
Collect 10000 gold
Find 6 secrets
Use a revive
Buy a level 6 skill with the Witch
Reach the floor 666 on DDD
Reach the floor 360 on DDD
Reach the floor 300 on DDD
Reach the floor 260 on DDD
Reach the floor 200 on DDD
Reach the floor 160 on DDD
Reach the floor 100 on DDD
Reach the floor 60 on DDD
Reach the floor 30 on DDD
Reach the floor 10 on DDD
Collect 5000 gold
Clear the Deepest Dungeons of Doom
Drink poison and die
Buy a level 6 skill with the Mercenary
Kill 1000 monsters
Taking more than 20 points of damage in one fight
Find 3 secrets
Find one secret
Kill 50 beast monsters
Collect 1000 gold
Slay the Icy Caves' boss while carrying no equipment
Completing a dungeon with 1 hp
Die on a dungeon first floor
Collect 500 gold
Clear 6 dungeons
Collect 300 gold
Kill 100 monsters
Die in a single hit with full health
Kill 50 human monsters
Kill 50 undead monsters
Use a revenge bonus
Die for the first time
Clear 3 dungeons
Kill a zombie
Clear the Sewer
Completing a dungeon without using any potions