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 Crusader 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
Buy all Mercenary skills
Buy a level 6 skill with the Mercenary
Buy all Witch skills
Collect 10000 gold
Completing a dungeon with 1 hp
Slay the Icy Caves' boss while carrying no equipment
Buy a level 6 skill with the Crusader
Find 10 secrets
Clear the Deepest Dungeons of Doom
Find 6 secrets
Buy a level 6 skill with the Witch
Collect 5000 gold
Find 3 secrets
Use a revive
Die on a dungeon first floor
Kill 1000 monsters
Die in a single hit with full health
Kill 50 beast monsters
Collect 1000 gold
Taking more than 20 points of damage in one fight
Drink poison and die
Collect 500 gold
Kill 50 human monsters
Kill 50 undead monsters
Kill 100 monsters
Clear 6 dungeons
Collect 300 gold
Clear 3 dungeons
Kill a zombie
Use a revenge bonus
Die for the first time
Find one secret
Completing a dungeon without using any potions
Clear the Sewer