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