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