Here is the full list of all 26 Slayin DX achievements.
Defeat the Mintoaur.
Defeat the Imp.
Defeat the Royal Slime.
Defeat Peloria.
Defeat the Death Wurm.
Defeat the Harpy.
Defeat the Spectral Rider.
Unlock all six characters.
Get a score of 50,000 or more points.
Get a score of 100,000 or more points.
Get a score of 150,000 or more points.
Buy any gameskin.
Buy any tombstone part.
Beat any 2 bosses without taking damage.
Get a x5 mutliplier.
Get a combo of 100.
Kill 5,000 enemies.
Kill 15,000 enemies.
Kill 50,000 enemies.
Collect 10,000 coins.
Collect 100 large coins.
Get 50,000 Fame Points.
Get 500,000 Fame Points.
Get 1,000,000 Fame Points.
Defeat the Dragon.
Finish Boss Rush mode.