Here is the full list of all 63 Pixel Dungeon achievements.
Item of level 3 acquired
15 monsters killed at nighttime
Death from fire
13 points of Strength attained
Collected 500 gold coins
10 enemies slain
Collected 100 gold coins
50 enemies slain
150 enemies slain
250 enemies slain
Collected 2500 gold coins
Collected 7500 gold coins
Level 6 reached
Level 12 reached
Level 18 reached
Level 24 reached
1st boss slain
2nd boss slain
3rd boss slain
4th boss slain
All potions identified
All scrolls identified
All rings identified
All wands identified
All potions, scrolls, rings & wands identified
All bags bought
Ring of Haggler obtained
Ring of Thorns obtained
Amulet of Yendor obtained
Amulet of Yendor obtained by Warrior, Mage, Rogue & Huntress
Pixel Dungeon left
Challenge won
Death from poison
Death from toxic gas
Death from hunger
Death from an enchantment
Death from falling down
Death from fire, poison, toxic gas & hunger
15 points of Strength attained
17 points of Strength attained
19 points of Strength attained
10 pieces of food eaten
20 pieces of food eaten
30 pieces of food eaten
40 pieces of food eaten
Item of level 6 acquired
Item of level 9 acquired
Item of level 12 acquired
3 potions cooked
6 potions cooked
9 potions cooked
12 potions cooked
10 games played
100 games played
500 games played
2000 games played
1st boss slain by Warrior, Mage, Rogue & Huntress
3rd boss slain by Gladiator, Berserker, Warlock, Battlemage, Freerunner, Assassin, Sniper & Warden
All rare monsters slain
7-hit combo
Level completed without killing any monsters
Monster killed by a Grim weapon
6 piranhas killed