Here is the full list of all 30 Pixel Slayer achievements.
Slay 10 monsters
Slay 100 monsters
Slay 1000 monsters
Slay 10000 monsters
Slay 100000 monsters
Play for 2 hours
Play for 4 hours
Play for 8 hours
Play for 16 hours
Play for 32 hours
Buy 5 upgrades
Buy 50 upgrades
Buy 500 upgrades
Buy 5000 upgrades
Buy 50000 upgrades
Collect 10 gold coins
Collect 100 gold coins
Collect 1000 gold coins
Collect 10000 gold coins
Collect 100000 gold coins
Complete the game once
Complete the game 2 times
Complete the game 3 times
Complete the game 4 times
Complete the game 5 times
Restart the game with prestige upgrades
Unlock the real ending
Make 10000 damage per one hit
Unlock all monsters
The fun starts in 3.. 2.. 1..