Here is the full list of all 15 Riddled Corpses achievements.
You killed the first boss and finished stage 1
Get 5 special items
Your first death
Jon now has max power. Now kill the undead!
Cloe now has max power. Now kill the undead!
Lieri now has max power. Now kill the undead!
Fael now has max power. Now kill the undead!
Erika now has max power. Now kill the undead!
Achieve level 130!
You killed the second boss and finished stage 2!
You killed the third boss and finished stage 3!
You killed the forth boss and finished stage 4!
You killed the fifth boss and finished stage 5!
You've finished all stages on arcade mode
Kill 50000 enemies in survival or arcade mode