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 a level 6 skill with the Mercenary
Buy all Witch skills
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
Causing more than 100 points of damage in one hit
Reach the floor 30 on DDD
Reach the floor 10 on DDD
Drink poison and die
Find 10 secrets
Collect 10000 gold
Clear the Deepest Dungeons of Doom
Buy a level 6 skill with the Crusader
Buy a level 6 skill with the Witch
Kill 1000 monsters
Taking more than 20 points of damage in one fight
Find 6 secrets
Kill 50 beast monsters
Use a revive
Collect 5000 gold
Find 3 secrets
Slay the Icy Caves' boss while carrying no equipment
Completing a dungeon with 1 hp
Die on a dungeon first floor
Die in a single hit with full health
Kill 50 undead monsters
Collect 1000 gold
Kill 50 human monsters
Kill 100 monsters
Find one secret
Collect 500 gold
Clear 6 dungeons
Collect 300 gold
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